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上海大学材料学院硕士培养方案

材料科学与工程专业攻读硕士学位研究生培养方案一、培养目标为适应我国国民经济发展和社会主义建设的需要，培养德、智、体全面发展的材料科学与工程学科高层次专门技术人才，本学科硕士研究生培养目标是：1．坚持党的基本路线，热爱祖国，尊纪守法，品德高尚，学风严谨，具有事业心和团队精神，立志为社会主义现代化建设事业服务。

2．在本门学科上掌握宽广的基础理论和系统的专门知识，熟练掌握一门外国语；具有从事材料科学与工程方面工作的研究与开发能力，以及独立担负专门技术工作的能力。

3．积极参加体育锻炼，身体健康。

二、学习年限硕士研究生的学习年限为二年半。

在职研究生的学习年限可适当延长半年至一年。

三、主要研究方向1．材料相变及热力学2．金属材料的强韧化3．金属及合金中氢的行为4．非晶、纳米晶和粉体材料制备及应用5．材料的腐蚀及防腐6．碳基复合材料7．晶界工程8．新型特种钢9．模具材料的研究与应用10．现代表面工程和技术11．汽车用钢板的研究与应用12．新型铝合金材料与成型技术13．铸造合金及凝固技术14．薄膜电子材料与器件15．信息功能复合材料及应用16．电子陶瓷材料的制备、性能研究及应用17．微电子材料物理与化学18．材料智能化、机敏化、智能结构与系统19．光电子材料及器件20．先进功能材料（如磁性材料、储能材料、超导材料、核反应堆材料、光催化环境净化材料等）四、课程设置（见表）五、论文工作1. 在课程修满48学分后，可申请进入论文课题研究，但也可根据导师的实际安排，入学后一边学习，一边逐渐进入课题工作；电子信息材料系的研究生在开题报告前应提交2篇与专业相关的科技综述报告。

2. 开题报告在第二学年第一学期进行，选题应与本专业的基础研究或国民经济中的重要问题相结合。

开题报告应在5000字以上，开题报告应包括发展现状、选题意义、研究内容、进度安排以及预期成果等。

开题报告应组织3名以上的高级职称教师进行评审，为公开性报告。

3. 在论文阶段的中期，进行阶段检查和期中考核，并做出书面论文阶段报告，报送上级管理部门，若离进度要求偏离较大予以黄牌警告。

高三英语材料科学单选题60题

高三英语材料科学单选题60题1.Metal is a common material in engineering. Which of the following is not a metal?A.ironB.aluminumC.glassD.copper答案：C。

本题考查材料科学中金属的概念。

铁（iron）、铝（aluminum）和铜（（copper）都是常见的金属。

而玻璃（（glass）是一种非金属材料，主要由硅酸盐等组成。

2.Which material is often used for insulation?A.steelB.plasticC.goldD.silver答案：B。

在材料科学中，塑料（（plastic）常被用作绝缘材料。

钢（steel）、金（（gold）和银（（silver）都是导电性能较好的金属材料，不适合用于绝缘。

3.In the field of materials science, which one is a composite material?A.woodB.paperC.concreteD.water答案：C。

混凝土（（concrete）是一种复合材料，由水泥、骨料和水等组成。

木头（（wood）是天然材料。

纸（（paper）主要由纤维素等组成，不是复合材料。

水（water）是一种化合物，不是复合材料。

4.Which material is known for its high hardness?A.rubberB.leatherC.diamondD.cloth答案：C。

在材料科学中，钻石（（diamond）以其高硬度而闻名。

橡胶（rubber）、皮革（leather）和布（cloth）的硬度都较低。

5.Which of the following materials is ductile?A.brickB.glassC.copperD.stone答案：C。

在材料科学中，铜（（copper）是一种具有延展性（（ductile）的金属材料。

学术英语理工第二版unit3课文原文

学术英语理工第二版unit3课文原文全文共10篇示例，供读者参考篇1Hello everybody, today I'm going to read you a story from our academic English textbook, unit 3. It's called "The Importance of Recycling". Let's get started!In our world, there are many things that we use every day, like paper, plastic, and glass. But do you know what happens to these things after we throw them away? That's where recycling comes in! Recycling is when we take used materials and turn them into new things. It's like giving old things a second chance to be useful again.Recycling is important for many reasons. One reason is that it helps to protect the environment. When we recycle, we save energy and reduce pollution. This means that we can help to keep our air and water clean for plants, animals, and humans.Another reason why recycling is important is that it helps to save natural resources. By reusing materials like paper and metal, we can prevent the need to cut down more trees or mine moreminerals from the earth. This is good for our planet because it helps to preserve our resources for future generations.So, next time you're done with a piece of paper or a plastic bottle, remember to put it in the recycling bin instead of the trash. By doing this simple act, you can help to make a big difference in the world. Let's all do our part to protect the environment and save our planet!I hope you enjoyed the story and learned something new about recycling. Remember, small actions can make a big impact. Thanks for listening!篇2Hi everyone, today I'm going to share with you the text from Unit 3 of the Academic English for Science and Engineering textbook.The text talks about a scientist named Marie Curie. She was a really smart lady who discovered two new elements called radium and polonium. Can you believe that? She won two Nobel Prizes for her amazing work in chemistry and physics. Wow, what a superstar!Marie Curie faced a lot of challenges in her life, but she never gave up. She was determined to keep learning and exploring the world of science. She even set up a research institute to help other scientists study radiation. She was definitely a role model for all of us.In the text, it also talks about the dangers of working with radiation. Marie Curie was exposed to radiation for many years, and unfortunately, it made her really sick. That's why it's so important for scientists to be careful when they're working with dangerous materials.I think Marie Curie's story is really inspiring. She showed us that with hard work and determination, we can achieve amazing things. I hope we can all learn from her example and never stop pursuing our dreams.So that's the text from Unit 3. I hope you enjoyed it! Let's all be like Marie Curie and keep pushing ourselves to reach new heights in our studies. See you next time! Bye!篇3Unit 3 Lesson 1: What Are Animals Like?Hey guys! Today we're gonna learn about animals in Unit 3 of our Science class! Animals are super cool, right? They come in all shapes and sizes, and live in different places. Let's dive into the world of animals and explore what they are like!First, we have mammals. Mammals are animals that have hair or fur on their bodies. They also give birth to live babies and feed them with milk. Examples of mammals are dogs, cats, and monkeys. They are so cute and fluffy!Next up, we have birds. Birds have feathers, beaks, and lay eggs. They also have wings that help them fly in the sky. Birds come in all colors and sizes, from tiny hummingbirds to big, majestic eagles. It's amazing to see them soar through the air!Then, we have reptiles. Reptiles are animals that have scales, and some of them have shells or plates. They lay eggs on land and most of them are cold-blooded, which means their body temperature changes with their environment. Examples of reptiles are snakes, turtles, and crocodiles. They might look scary, but they're actually pretty cool!After that, we have amphibians. Amphibians are animals that live both on land and in water. They have moist skin and most of them lay eggs in water. Frogs and salamanders are examples of amphibians. They can jump really high and swim super fast!Last but not least, we have fish. Fish have fins, scales, and gills that help them breathe underwater. They come in all kinds of shapes, colors, and sizes. From tiny goldfish to giant whales, fish are truly fascinating creatures of the sea.Wow, learning about animals is so much fun, right? They have different features and behaviors that make them unique. So next time you see an animal, take a moment to appreciate how amazing they are! Keep exploring the world of animals, and let's continue to learn and grow together. Stay curious and keep on shining bright like the stars! See you next time, bye!篇4Hello everyone, today I'm going to share with you the text from Unit 3 of the book "Academic English for Science and Engineering Second Edition". Let's get started!The text is all about renewable energy, which is super important for the environment. It talks about different types of renewable energy like wind power, solar power, and hydropower. These are all sources of clean energy that don't harm the planet like fossil fuels do.Did you know that wind power is created by wind turbines? They look like big fans and they spin around to generateelectricity. Solar power comes from the sun, which is pretty cool. And hydropower is made from water flowing through dams to create energy.Renewable energy is great because it's sustainable, which means we can keep using it without running out. Plus, it helps to reduce pollution and greenhouse gas emissions, which is awin-win for the planet!I hope you learned something new from this text. Let's all do our part to support renewable energy and take care of our Earth. Thanks for listening!篇5Unit 3 Our EarthHi everyone, today let's learn about our Earth! Our Earth is a super cool place filled with all kinds of amazing things. It's the planet we live on, and we need to take care of it.First, let's talk about the Earth's crust. The Earth's crust is like the outer skin of our planet. It's made up of different layers and it's super tough. Sometimes the Earth's crust moves around, causing earthquakes and volcanoes. It's important to be prepared for these natural disasters.Next, let's talk about the Earth's atmosphere. The Earth's atmosphere is the air around us. It's made up of different gases like oxygen and carbon dioxide. Plants need carbon dioxide to photosynthesize and give us oxygen to breathe. So, it's really important to take care of our plants and trees.Now, let's talk about the Earth's water. The Earth has lots of water in the oceans, rivers, lakes, and even in the air as clouds. Water is super important for all living things, like plants and animals. We should all try to save water and not waste it.Last but not least, let's talk about the Earth's resources. The Earth gives us so many resources like minerals, metals, and fossil fuels. It's important to use these resources wisely and not waste them. We should also try to find renewable sources of energy, like solar and wind power.In conclusion, our Earth is an amazing place that we need to take care of. Let's all do our part to protect our planet and make it a better place for future generations. Remember, we only have one Earth, so let's cherish it and keep it clean and healthy. Thank you for listening!篇6Unit 3Hello everyone, today we are going to learn about a new unit in our Science and Technology textbook. In this unit, we will explore the topic of the Earth's atmosphere and weather.The atmosphere is like a big blanket that surrounds the Earth. It is made up of different gases like nitrogen, oxygen, and carbon dioxide. These gases are important because they help to keep the Earth warm and protect us from harmful rays from the sun.Have you ever wondered why it rains or snows? Well, it's all because of the weather! The weather is made up of different factors like temperature, humidity, and air pressure. When these factors change, it can cause different types of weather like rain, wind, or snow.Do you know what a thermometer is used for? It's a tool that measures the temperature of the air. Scientists use thermometers to help them study the weather and predict what it will be like in the future.Another important tool that scientists use is a barometer. This measures the air pressure, which can tell us if a storm is coming or if the weather will be clear and sunny.So, the next time you look up at the sky, remember that there is a lot happening in the atmosphere above us. By learningabout the Earth's atmosphere and weather, we can better understand the world around us. Isn't that cool? Let's keep exploring and learning more about science and technology!篇7Hello everyone! Today, I'm going to share with you the text from the book "Academic English for Science and Engineering Second Edition Unit 3". It's all about different kinds of energy and how they are used in our daily lives. Let's get started!The first type of energy we will talk about is mechanical energy. Mechanical energy is the energy that an object has because of its motion or position. For example, when you kick a soccer ball, the energy from your leg is transferred to the ball, causing it to move. It's like magic, but it's actually science!Next up is thermal energy. Thermal energy is the energy that comes from heat. When you cook food on the stove, the heat is transferred from the stove to the food, making it hot and yummy. Without thermal energy, we wouldn't be able to cook our favorite meals or stay warm in the winter.Now, let's talk about electrical energy. Electrical energy is the energy that comes from the flow of electrons. It powers ourphones, computers, and lights. Can you imagine a world without electricity? It would be so boring and dark!Last but not least, we have chemical energy. Chemical energy is the energy stored in the bonds between atoms and molecules. When you eat food, your body breaks down the chemical bonds to release energy, which gives you the energy to run and play.So, there you have it! Different types of energy that make our world go round. Remember, energy is all around us and it's up to us to use it wisely. Thanks for listening, and I hope you learned something new today!篇8Unit 3 Lesson 1: Living ThingsHey there! Today we are going to learn all about living things. Living things are everywhere around us. Plants, animals, and even you and me are all living things!Plants are living things that make their own food through a process called photosynthesis. They use sunlight, water, and carbon dioxide to make their own food. Plants also help us breathe by releasing oxygen into the air.Animals are another type of living thing. They need to eat food to survive. Some animals eat plants, some animals eat other animals, and some eat both! Animals also move around and grow, just like us.Humans are also living things. We need to eat, drink, breathe, and sleep to stay healthy. We have different organs in our bodies that help us do these things. Our heart pumps blood, our lungs help us breathe, and our brain helps us think and learn.There are so many different living things in the world, big and small. Some live on land, some live in the water, and some even fly in the sky! Living things come in all shapes, sizes, and colors.So, next time you see a plant, an animal, or even yourself in the mirror, remember that we are all living things. Let's take care of each other and the environment around us. Happy learning!篇9Unit 3 SharingHello everyone! Today, we are going to learn about sharing. Sharing is a very important thing to do because it makes otherpeople happy. When you share with others, you are being kind and thoughtful.Sharing can be done in many ways. You can share your toys with your friends, share your snacks with your classmates, or share your ideas with your family. By sharing, you are showing that you care about others and that you are willing to help them.When you share, you are also learning how to cooperate and work together. Sharing helps build strong relationships and friendships. It also teaches you to be generous and considerate.In school, we share things all the time. We share our pencils and erasers with our classmates. We share our books and papers with our friends. We also share our knowledge and ideas with our teachers and classmates.Sharing is not just about giving things away. It is also about listening and being open to other people's ideas. When you share, you are creating a positive and supportive environment.So, let's remember to share with others and show them kindness and respect. Let's work together and make the world a better place for everyone. Share the love and spread happiness! Thank you for listening and remember, sharing is caring!篇10Unit 3 Our EnvironmentHi everyone, today we're going to learn about our environment! Our environment is super important because it's where we live and play every day. We want to keep our environment clean and healthy so that we can all be happy and safe.First, let's talk about air pollution. Air pollution is when there are dirty things in the air that can hurt our lungs and make us sick. Some things that cause air pollution are cars, factories, and even just burning things like trash. We can help reduce air pollution by walking or biking instead of driving, and by picking up trash so it doesn't get burned.Next, let's chat about water pollution. Water pollution happens when dirty things get into our rivers, lakes, and oceans. This can make the water unsafe for us to drink and for animals to live in. We can help prevent water pollution by not dumping chemicals down the drain and by picking up trash near water sources.Lastly, let's touch on land pollution. Land pollution is when we litter and leave trash on the ground instead of throwing it away properly. This can harm animals and plants that live in the environment. We can help stop land pollution by alwaysthrowing our trash in the trash cans and by recycling things like bottles and cans.Remember, it's super duper important to take care of our environment so that it stays clean and healthy for all of us. Let's work together to make our world a better place!。

英文审稿意见汇总(最新整理)

1、目标和结果不清晰。

It is noted that your manuscript needs careful editing by someone with expertise in technical English editing paying particular attention to English grammar, spelling, and sentence structure so that the goals and results of the study are clear to the reader.2、未解释研究方法或解释不充分。

◆In general, there is a lack of explanation of replicates and statistical methods used in the study.◆Furthermore, an explanation of why the authors did these various experimentsshould be provided.3、对于研究设计的rationale:Also, there are few explanations of the rationale for the study design.4、夸张地陈述结论/夸大成果/不严谨：The conclusions are overstated. For example, the study did not showif the side effects from initial copper burst can be avoid with the polymer formulation.5、对hypothesis的清晰界定：A hypothesis needs to be presented。

6、对某个概念或工具使用的rationale/定义概念：What was the rationale for the film/SBF volume ratio?7、对研究问题的定义：Try to set the problem discussed in this paper in more clear,write one section to define the problem8、如何凸现原创性以及如何充分地写literature review:The topic is novel but the application proposed is not so novel.9、对claim,如A＞B的证明，verification:There is no experimental comparison of the algorithm with previously known work, so it is impossible to judge whether the algorithm is an improvement on previous work.10、严谨度问题：MNQ is easier than the primitive PNQS, how to prove that.11、格式（重视程度）：◆In addition, the list of references is not in our style. It is close but not completely correct. I have attached a pdf file with "Instructions for Authors" which shows examples.◆Before submitting a revision be sure that your material is properly prepared and formatted. If you are unsure, please consult the formatting nstructions to authors that are given under the "Instructions and Forms" button in he upper right-hand corner of the screen.12、语言问题（出现最多的问题）：有关语言的审稿人意见：◆It is noted that your manuscript needs careful editing by someone with expertise in technical English editing paying particular attention to English grammar, spelling, and sentence structure so that the goals and results of the study are clear to the reader.◆The authors must have their work reviewed by a proper translation/reviewing service before submission; only then can a proper review be performed. Most sentences contain grammatical and/or spelling mistakes or are not complete sentences.◆As presented, the writing is not acceptable for the journal. There areproblems with sentence structure, verb tense, and clause construction.◆The English of your manuscript must be improved before resubmission. We strongly suggest that you obtain assistance from a colleague who is well-versed in English or whose native language is English.◆Please have someone competent in the English language and the subject matter of your paper go over the paper and correct it. ?◆the quality of English needs improving.来自编辑的鼓励：Encouragement from reviewers:◆I would be very glad to re-review the paper in greater depth once it has been edited because the subject is interesting.◆There is continued interest in your manuscript titled "……" which you submitted to the Journal of Biomedical Materials Research: Part B - AppliedBiomaterials.◆The Submission has been greatly improved and is worthy of publication.∙The paper is very annoying to read as it is riddled with grammatical errors and poorly constructed sentences. Furthermore, the novelty and motivation of the work is not well justified. Also, the experimental study is shallow. In fact, I cant figure out the legends as it is too small! How does your effort compares with state-of-the-art?∙The experiment is the major problem in the paper. Not only the dataset is not published, but also the description is very rough. It is impossible to replicate the experiment and verify the claim of the author. Furthermore, almost no discussion for the experimental result is given. E.g. why the author would obtain this result? Which component is the most important? Any further improvement?∙the author should concentrated on the new algorithm with your idea and explained its advantages clearly with a most simple words.∙it is good concept, but need to polish layout, language.∙The authors did a good job in motivating the problem studied in theintroduction. The mathematic explanation of the proposed solutions is also nice. Furthermore, the paper is accompanied by an adequate set of experiments for evaluating the effectiveness of the solutions the authors propose.Apparently，Obviously ,Innovation ,refine ,In my humble opinion如果仍然有需要修改的小毛病，一般你可以用you paper has been conditionally accepted. Please revise .....according to review comments.如果是接受，你可以用We are very pleased to inform you that your paper "xxxxx" has been accepted by [journal name]. Please prepare your paper by journal template...............At a first glance, this short manuscript seems an interesting piece of work, reporting on ×××. Fine, good quality, but all this has been done and published, and nearly become a well-known phenomenon. Therefore, there is insufficient novelty or significance to meet publication criteria. Also, I did not see any expermental evidence how the ** is related with **, except for the hand-waving qualitative discussion. Therefore, I cannot support its publication in JPD in its present form. It should be rejected.建议去小木虫问问，那里有一些资源。

section2 1-4科技英语阅读与翻译

1 Monograph专著1. The general definition of a monographScientific treatises of book length but otherwise variable format prepared by acknowledged experts onspecialized topics for the benefit of others who have specialized in. or who wish to obtain a specialist'sappreciation of, these topics.2. The value of monographs for scientific researchesThe value of monographs lies in the coherence and comprehensiveness of the information and knowledge theycontain, which is important to the specialized researchers to whom they are directed and, therefore, to theadvancement of science and engineering generally.3. The qualities of the authors of monographsThe authors of monographs should have exceptional breadth and depth of knowledge, and must be able tocollect, collate, analyze, integrate, and synthesize all relevant contributions to the archival literature of thescientific and engineering journals and to add original material as required.4. The differences between monographs and books of conference proceedingsMonographs generally are written by specialists for the benefit of other specialists. Textbooks are pedagogicalworks which, even if written on fairly narrow subjects, are designed to serve broader and more juniorreaderships than specialized research communities.5. The differences between monographs and books of conference proceedingsConference papers commonly take the form of premature announcements of new scientific discoveries.Conference proceedings generally have a short shelf life.6. The main components of a monographThe author, title and subtitle, date of publication, dust cover or blurb, content pages, bibliography and index,illustrations, preface and introduction.7. An indication of the book’s successThe number of editions is an indic ation of the book’s success.8. The function of the blurbIt gives the reader a rapid overview of the contents and approach. It might also say what the book contains andfor whom it is written.2 Academic Journal学术期刊1. The general definition of an academic journalAn academic journal is a peer-reviewed periodical in which scholarship relating to a particular academicdiscipline is published.2. The significance of peer-review processThe peer-review process is considered critical to establishing a reliable body of research and knowledge.3. The definition of review articlesReview articles, also called “reviews of progress”, are checks on the research published in journals.4. One difference between original research articles and review articlesUnlike original research articles, review articles tend to be solicited submissions, sometimes planned years inadvance.5. The places where science journals are authoritatively rankedNatural science journals are categorized and ranked in the Science Citation Index, and social science journalsin the Social Science Citation Index.6. The possible quantitative factors to reflect an academic journal’s prestigeThe number of later articles citing articles already published in the journal, the overall number of citations,how quickly articles are cited, and the average “half-life” of articles.7. The financial resources of humanities and social science academic journalsSubsidies by universities or professional organizations and advertising fees by advertisers.8. The role of internet in the production of, and access to, academic journalsThe Internet has revolutionized the production of, and access to, academic journals, with their contentsavailable online via services subscribed to by academic libraries or even in a way of open access. 33 Organization of a Scientific Paper科技论文的篇章结构1. In most scientific journals, scientific papers include the following sectionsSummary or Abstract, Introduction, Materials and Methods, Results, Discussion, Acknowledgments.2. The content of Summary or AbstractIt gives a brief background to the topic, describes concisely the major findings of the paper, and relates thesefindings to the field of study.3. The Introduction section deals with the following two pointsIt describes first the accepted state of knowledge in a specialized field; then it focuses more specifically on aparticular aspect, usually describing a finding or set of findings that led directly to the work described in thepaper.4. The purpose of Materials and MethodsIts purpose is to describe the materials used in the experiments and the methods by which the experimentswere carried out.5. The two ways of organizing ResultsIn some papers, the results are presented without extensive discussion, which is reserved for thefollowingsection. In other papers, results are given, and then they are interpreted, perhaps taken together with otherfindings not in the paper, so as to give the logical basis for later experiments.6. The purposes of the Discussion sectionThe data in the paper are interpreted; the findings of the paper are related to other findings in the field; thisserves to show how the findings contribute to knowledge, or correct the errors of previous work; some of thelogical arguments are often provided when it is necessary to clarify why later experiments were earned out.7. The reason for combining the Results and DiscussionBecause the data need extensive discussion to allow the reader to follow the train of logic developed in thecourse of the research.8. The difference between the abstracts in Science and those in NatureIn Science, the abstract is self-contained; in Nature, the abstract also serves as a brief introduction to the paper.4 Reading a Scientific Paper科技论文的阅读方法1. The order to understand the major points of the work, you should first readThe Abstract.2. Reading the Title and the Abstract serves three purposesFirst, it clarifies whether you in fact know enough background to appreciate the paper. Second, it refreshesyour memory about the topic. Third, it helps you integrate the new information into your previous knowledgeabout the topic.3. When reading in a familiar field, you can skim or even skipThe Introduction.4. The three typical codewordsData not shown, unpublished data, preliminary data.5. The poorly written papers are often related to three types of writersThose who are poor writers; those who do not enjoy writing, and do not take the time or effort to ensure thatthe prose is dear and logical; those who are so familiar with the material that it is difficult to step back and seeit from the point of view of a reader not familiar with the topic.6. The three characteristics of “bad writing”First, the logical connections are often left out. Second, papers are often cluttered with a great deal of jargon.Third, the authors often do not provide a clear roadmap through the paper.7. In better writing, the side issues are dealt with in the following waysThey are relegated to Figure legends or Materials and Methods or clearly identified as side issues, so as not todistract the reader.8. Another problem faced by the readers is that when they seek to understand just the experiment was,they may findThe authors refer back to previous papers; these refer in turn to previous papers m a long chain.。

材料制备技术论文

材料制备技术论文材料制备技术课程是金属材料工程专业的一门专业必修课,内容多而杂,相互之间无连贯性,并且实践性强,存在着一定的教学难度。

这是店铺为大家整理的材料制备技术论文，仅供参考!材料制备技术论文篇一块状金属纳米材料的制备技术进展及展望摘要综述了国内外块状纳米材料的制备技术进展及存在的问题。

提出了超短时脉冲电流直接晶化法和深过冷直接晶化法两类潜在的块状金属纳米晶制备技术，并对今后的研究及发展前景进行了展望。

关键词纳米晶块体材料制备非晶晶化机械合金化深过冷DEVELOPMENT OF BULK METAL NANOMETER MATERIALS PREPARATION TECHNOLOGIES AND THEiR ESTIMATEABSTRACT On the basis of the summarization of bulk metal nanocrystalline materials preparation methods,two potential technologies:super short false current direct crystallization method and high undercooling direct crystallization method are proposed.In the end,the development and application prospects of various methods are also estimated.KEYWORDS bulk nanometer material,preparation of materials,crystallization of amorphous alloys,mechanical alloying,high undercoolingCorrespondent:Zhang Zhenzhong Northwestern Polytechnical University,State key Laborotry of Solidification Processing Xi'an 710072自80年代初德国科学家H.V.GlEIter成功地采用惰性气体凝聚原位加压法制得纯物质的块状纳米材料后[1]，纳米材料的研究及其制备技术在近年来引起了世界各国的普遍重视。

Materials-Letters-详细投稿指南

以下是Materials Letters的作者指南，我觉得它已经非常简明的说清楚整个投稿过程需要注意的东西2009年影响因子：1.94Guide for Authors Materials LettersMaterials Letters is dedicated to publishing novel, cutting edge reports of broad interest to the materials community. The journal provides a forum for materials scientists and engineers, physicists, and chemists to rapidly communicate on the most important topics in the field in materials. We are primarily interested in those contributions which bring new insights, and papers will be selected on the basis of the importance of the new knowledge they provide.Contributions include a variety of topics such as:• Materials- Metals and alloys, amorphous solids, ceramics, composites, nanocrystals, polymers, semiconductors.• Applications - Structural, opto-electronic, magnetic, medical, MEMS, sensors, smart.• Characterization- Analytical, microscopy, scanning probes, nanoscopic, optical, electrical, acoustic, spectroscopic, diffraction.• Novel Materials- Micro and nanostructures (nanowires, nanotubes, nanoparticles), nanocomposites, thin films, superlattices, quantum dots.• Processing - Thin film processing, sol-gel processing, mechanical processing, assembly, and nanocrystalline processing leading to unique materials.• Properties - Mechanical, magnetic, optical, electrical, ferroelectric, thermal, interfacial, transport, thermodynamic.• Synthesis- Quenching, solid state, solidification, solution synthesis, vapor deposition, and high pressure, explosive processes leading to unique materials. The following topics are inappropriate for publication:Building materials - aggregate, asphalt, cement, concrete, plasterCatalytic materialsCorrosion and oxidation phenomena and protectionLiquid crystalsMetallurgical ProcessesNatural raw materials – clays, minerals, rocksOxide glasses and glass ceramicsRecycled materialsRefractoriesSingle crystal growthTheoryWearTypes of Contribution:Letters are intended as brief reports of significant, original and timely research results on the science, applications and processing of materials which warrant rapid publication. In considering a manuscript for publication, particular attention will be given to the originality of the research, the desirability of speedy publication, the clarity of the presentation and the validity of the conclusions. There is a strict four-page limit to printed articles. Manuscripts must not exceed 2000 words plus three figures and one table. The maximum number of figures is strictly limited to five. 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The PDF a watermarked version of the published article and includes a cover sheet with the journal cover image and a disclaimer outlining the terms and conditions of use. Keyword List（被省略）。

学术英语(理工)-Unit 2

to get the materials
• Using the library Getting to know the library organization: Circulation desk Reference room Card catalog Computer facilities Photocopiers Non-print materials
学术英语理工
Academic English
for Science and Engineering
Unit 2 Searching for Information
t Contents
1 Finding reliable and better sources
2 Scanning and skimming
(Educational resources information center)
• Online magazines or newspapers
Searching on the internet
• Online discussion groups • Online journals
• • • • • • • Search engines you should know:
Searching on the internet
3 Identifying topic sentences for information 4 Guessing word meaning 5 Using the organization of the text 6 Reading critically
7 Taking notes
8 Writing a summary

Effects of heat treatments on the microstructure and mechanical properties of a 6061 aluminium alloy

Materials Science and Engineering A 528 (2011) 2718–2724Contents lists available at ScienceDirectMaterials Science and EngineeringAj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /m s eaEffects of heat treatments on the microstructure and mechanical properties of a 6061aluminium alloyD.Maisonnette a ,M.Suery b ,D.Nelias a ,∗,P.Chaudet a ,T.Epicier caUniversitéde Lyon,CNRS,INSA-Lyon,LaMCoS UMR5259,F-69621,FrancebUniversitéde Grenoble,SIMaP,UMR CNRS 5266,BP46,Domaine Universitaire,38402Saint Martin d’Hères Cedex,France cUniversitéde Lyon,CNRS,INSA-Lyon,Mateis UMR5510,F-69621,Francea r t i c l e i n f o Article history:Received 23August 2010Received in revised form 3December 2010Accepted 3December 2010Available online 9 December 2010Keywords:6061Aluminium alloyThermomechanical propertiesElectron beam welding stress–strain curves Yield stressHardening precipitatesa b s t r a c tThis paper describes the mechanical behavior of the 6061-T6aluminium alloy at room temperature for various previous thermal histories representative of an electron beam welding.A fast-heating device has been designed to control and apply thermal loadings on tensile specimens.Tensile tests show that the yield stress at ambient temperature decreases if the maximum temperature reached increases or if the heating rate decreases.This variation of the mechanical properties is the result of microstructural changes which have been observed by Transmission Electron Microscopy (TEM).© 2010 Elsevier B.V. All rights reserved.1.IntroductionThe study presented in this paper is concerned with the widely used 6061-T6aluminium alloy.It is an age hardenable alloy,the mechanical properties of which being mainly controlled by the hardening precipitates contained in the material.When the material is subjected to a solution heat treatment followed by a quenching and a tempering treatment,its mechanical properties reach their highest level and become very good compared to other aluminium alloys.The as-obtained microstructure of the material is called T6temper (tempering around 175◦C).Another interest-ing characteristic of the AA6061is its good weldability.Because of these favorable properties,the AA6061alloy is used in the trans-port and the public works domains (framework,pylon,handling equipment ...)and also for complex structures assembled by weld-ing [1–3].The present work is part of the early qualifying study of a pres-sure vessel to be used in an experimental nuclear reactor.The approximate size of the vessel is ﬁve meters height with a diameter of about one meter.Several ferrules in AA6061-T6should be assem-bled together by electron beam (EB)welding.The aim of the work presented in this paper is to evaluate the inﬂuence of the weld-ing process on the mechanical properties of the material at room∗Corresponding author.E-mail address:daniel.nelias@insa-lyon.fr (D.Nelias).temperature.The change of mechanical properties is due to met-allurgical phenomena such as dissolution,growth or coarsening of precipitates,which have been also observed.It is commonly assumed that the generic precipitation sequence in Al–Mg–Si alloys is [4,5]:SSSS →GP →␤→␤→␤-Mg 2Si(1)Here SSSS represents the super-saturated solid solution and GP stands for Guinier–Preston zones.The sequence (1)will be consid-ered in this work.However,some authors give more details about this sequence [5–12]particularly Ravi and Wolverton [5]who gave a detailed inventory of the compositions of the phases contained in an Al–Mg–Si alloy.The compositions generally accepted for the most common precipitates are listed in Table 1.According to the literature [6–9,13,14],the T6temper of the 6XXX alloys involves very thin precipitates.They are ␤ needle-shaped precipitates oriented along the three 100 directions of the matrix.Their size is nanometric and they are partially coherent.The study presented in this paper includes High Resolution Transmission Electron Microscopy (HRTEM)observations of the investigated 6061-T6alloy in order to characterize the precipita-tion state of the T6temper.These observations will allow deﬁning a precipitate distribution of reference for the initial alloy.From this initial state,thermal loadings are applied on specimens which are thereafter observed by TEM.The investigated thermal loadings will also be applied on tensile specimens in order to evaluate the variation of the resulting mechanical properties.0921-5093/$–see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.msea.2010.12.011D.Maisonnette et al./Materials Science and Engineering A528 (2011) 2718–27242719Table1Compositions of the precipitates contained in Al–Mg–Si alloys.Phase CompositionGP zone Mg1Si1␤ Mg5Si6␤ Mg9Si5␤Mg2SiFor experimental convenience,the study will be limited to the solid state of the alloy.This means that the maximum temperature to be used is below582◦C(solidus temperature for the AA6061)and the phenomena occurring in the melting pool of the weld will not be taken into account here.Furthermore,the mechanical characteriza-tions and microstructural observations will be carried out at room temperature after the thermal loading.This will allow the char-acterization of the material at various points of the Heat Affected Zone(HAZ)after welding(and not during the welding process). For that purpose,the required thermal loadings should reproduce the temperature evolution in the HAZ with high heating rates up to200K/s.An experimental device has been speciﬁcally developed to meet these requirements.Atﬁrst,the design of the device will be brieﬂy presented.Then,the results of the mechanical charac-terizations and microstructural observations will be presented and discussed.2.Experimental procedure2.1.Experimental heating deviceThe main purpose of the experimental heating device is to repro-duce on a tensile specimen the thermal history encountered by each point of the heat affected zone during welding of the vessel.The highest temperature to be studied is thus T=560◦C,very close to the solidus temperature of582◦C which should not be reached.To do so,an accurate control of the temperature has been set up.Fur-thermore,the device should be able to reproduce the heating rate observed in the HAZ of an electron beam welding(up to200K/s). This heating rate has been evaluated by measuring it during an instrumented welding experiment.The second aim of the device is to apply a mechanical loading on a specimen in order to mea-sure the mechanical properties of the material.The mechanical and thermal loadings have to be used simultaneously in order to perform tensile tests at high temperature for further study or to compensate for thermal expansion of the specimen during heating. Therefore,the experimental equipment includes a heating device and a mechanical testing machine.2.1.1.Design of the deviceA convenient method to heat aluminium alloys at very high rate is by Joule effect.Another way would be by induction heating but it is not efﬁcient enough to obtain the required heating rate on alu-minium alloys.For this reason,a resistive heating device has been designed and constructed.In order to measure the temperature of the specimen during heating,a thermocouple has been spot welded on the specimen surface.The strains are measured by means of an extensometer with ceramic tips.The Joule heating device is a power supply,made of an electrical transformer and a thyristor bridge,providing a continuous current whose intensity is controlled by a thermal controller.Water cooled cables and clamping systems are used to connect the specimen to the heating device.A graphite resistor is added in series in order to increase the potential difference across the generator allowing a good temperaturecontrol.Fig.1.Temperature distribution measured by thermocouples along the tensile specimen.2.1.2.Specimen designA specimen heated by using Joule effect reacts as an electrical resistor.Its electrical resistance depends on the material electri-cal resistivity and the specimen shape which has to be optimized in order to reach the desired heating rate(up to500K/s).More-over,the temperature must be uniform over the measurement area (between the extensometer tips)and the specimen volume should be large enough for the microstructure to be representative of the alloy in real structures.A FEM simulation was performed to optimize the size and shape of the specimen.The used software,called Sysweld®was devel-oped by ESI Group.The simulation is carried out by using an electro kinetic model[15].The density d and the thermal conductivity K of the alloy were considered to vary with temperature.A paramet-ric study shows that a diameter of6mm is required to obtain a heating rate up to500K/s.A specimen length of100mm is also required to have a low thermal gradient.Fig.1shows the tempera-ture distribution in the specimen.The gradient has been measured with10thermocouples placed all over the length of a specimen peak-heated to350◦C at a heating rate of15K/s.2.1.3.Regulation set-upThe experimental device has been designed to reach high heat-ing rates.An accurate control of the temperature is required in order to avoid overshoots.To do so,a PID controller has been used [16–19].The resulting thermal loading is slightly delayed but the heating rate is equal to the desired one.The cooling rate is maxi-mum at the highest temperature(of the order of23K/s at500◦C) and decreases during cooling;it drops to about6K/s when temper-ature becomes lower than150◦C.2.2.Transmission Electron MicroscopyThe experimental device presented previously has been used to heat specimens for both mechanical measurements and TEM observations.Two types of microstructural observations have been carried out during this work.Theﬁrst one is a detailed observation of the microstructure of the material in the T6temper by means of HRTEM(High Resolution Transmission Electron Microscopy) and the second one by means of classical TEM to compare the microstructure of the alloy for three different states of precipita-tion.They were conducted on a JEOL2010F microscope operating at200kV,which belongs to the Centre Lyonnais de Microscopie (CLYM)located at INSA Lyon(France).TEM allows only very local observations so it was not intended to measure accurately the volume fraction of the precipitates;also not enough precipitates were analyzed to obtain an accurate mean radius.2720 D.Maisonnette et al./Materials Science and Engineering A528 (2011) 2718–2724The samples used in TEM are thin lamellas.A disk with a thick-ness of about200␮m is extracted from the heated specimen by means of a diamond wire saw.Its diameter is then reduced by punching.The disk is thinned to electron transparency(thickness to about200nm or less)by electropolishing using an electrolytic bath composed of20%of HNO3in methanol.The bath is cooled at−30◦C with liquid nitrogen[20].A Precision Ion Polishing System(PIPS) is used in order to accomplishﬁnal thinning and cleaning by ion milling.Some EDX(Energy-dispersive X-ray spectroscopy)analy-sis were performed with an Oxford Instruments analyzer,using a nanoprobe(about3nm in diameter)in the TEM to estimate the composition of the precipitates in the T6state.2.3.Mechanical characterizationTensile tests have been carried out at room temperature on spec-imens previously heated to peak temperatures of200,300,400,500 and560◦C with various heating rates(0.5,5,15,50,200K/s)in order to measure their mechanical properties.The thermal loadings are representative of the thermal histories encountered in EB welding.Three parameters have been investigated.Theﬁrst one is the maximum temperature reached during heating at a given heating rate(r=15K/s).The second one is the heating rate for a given max-imum temperature(T=400◦C).The third one is the dwell time at T=560◦C.This last study is not representative of a welding opera-tion but will allow understanding the variation of the mechanical characteristics during holding at a given temperature which cor-responds to the solution treatment of the alloy.For each test,the specimen is heated to the required temperature while compensat-ing for thermal expansion,then it is cooled to room temperature andﬁnally deformed until fracture at a strain rate of10−2s−1.Dur-ing the test,for a strain close to1.5%,an unloading is performed to measure the elastic modulus.3.Results3.1.HRTEM observations of the material in the T6temperThe aim of the HRTEM investigation on the AA6061-T6is to mea-sure the size of some hardening precipitates and to evaluate their composition in order to characterize the microstructure of the ref-erence T6state.The precipitates present in this state are hard to see owing to their very small size and because they are partly coherent with the aluminium matrix.HRTEM is thus mandatory to image the precipitates.Fig.2(a)shows a TEM picture at high magniﬁcation.Two needle-shaped precipitates can be seen:•Theﬁrst one is oriented along the[001]direction.Its cross sec-tion is observed making its diameter measurable accurately.The measure gives a diameter of about4nm.•The second one is oriented along the[100]direction.It is observed lying in the thin foil.The diffractogram,obtained by using Fourier transform,asso-ciated to theﬁrst precipitate is shown in Fig.2(b).In addition to the{200}diffraction spots associated with the aluminium matrix, weak aligned spots prove that the atomic state is partially disor-dered as for pre-␤ phases.At last,an EDX analysis carried out on the needle-shaped precip-itates by means of a3nm probe gives an atomic ratio X Mg/X Si=1.29 (with a standard deviation of0.3).This value is the average result of measurements onﬁve precipitates.3.2.Classical TEM observations of the microstructural changesFollowing the detailed study of the T6temper,the precipitates for various states were observed by means of classical TEM.The aim is to evaluate the evolution of the microstructure(size and vol-ume fraction of precipitates)as a function of the thermal loading previously submitted to the pared to HRTEM,classi-cal TEM is a better way to evaluate the volume fraction because it allows a larger area to be observed at lower magniﬁcation.How-ever classical TEM is worse than HRTEM to measure accurately the diameter of the precipitates because the images at high magniﬁca-tion are often fuzzy(a difﬁculty inherent to the diffraction contrast in conventional TEM).parison of three precipitation statesThe reference microstructure of the T6temper is here compared to states observed after a heating up to300◦C and400◦C at a heat-ing rate of15K/s and no dwell time at the maximum temperature.Fig.3shows three micrographs obtained from representative sample areas for the three investigated states.In the case of the specimen heated to400◦C,some precipitates with a needle shape are present in the picture.These precipitates are very large,with length between65and170nm and a mean value of112nm,and their diameter ranges between5and11nm with a mean value of 7.35nm.The mean values are calculated by taking into account ten precipitates observed on different pictures.However it should be mentioned that the precipitates could be cut by the sample prepa-ration,consequently the length given above should be considered as indicative only.They will be used to compare the precipitation state.In the two other cases,the precipitates are smaller.Their length is between20and40nm with a mean value of29nm for the T6 temper and between15and40nm with a mean value of25nm for the specimen heated to300◦C.Their diameter ranges between 3.75and4.6nm with a mean value of4.45nm for the T6temper and between2and4nm with a mean value of2.6nm for the specimen heated to300◦C.3.2.2.Precipitate volume fraction evaluationThe precipitate size can be measured by means of TEM pictures. However,it is much more difﬁcult to determine the precipitate volume fraction.Indeed,projections obtained by TEM correspond to volumetric observations but the thickness of the sample is not known accurately.In order to get a rough estimate of the precipi-tate volume fraction,TEM micrographs were compared to pictures obtained by modeling.A computer software has thus been devel-oped in Matlab to simulate these images.Based on three simple parameters describing the precipitation state,the program can reproduce a needle-shaped precipitate distribution in a sample with a uniform thickness.The three parameters are the volume fraction(f v),the mean radius of the needle precipitates(r avg)and their mean length(L avg).A Gaussian size distribution is arbitrarily assumed for the radius and the length with a variance of1and36,respectively.The size distributions are discretized in one hundred classes of size.Once the thickness isﬁxed(illustrations will be given here for a100nm thick material),the total volume is calculated and an iterative algo-rithm increases step by step the number of precipitates in each class to obtain the volume corresponding to the desired f v.The pre-cipitates are then shown graphically on a2D view by distributing them uniformly along the three 001 directions of the Al-matrix, which corresponds to the viewing directions of the TEM micro-graphs shown in Figs.2and3.Fig.4compares the precipitation state observed in the specimen heated to300◦C to two modeled states,theﬁrst one with a volume fraction of3%(Fig.4(a))and the second one with a volume fraction of1.6%(Fig.4(c)).It clearlyD.Maisonnette et al./Materials Science and Engineering A528 (2011) 2718–27242721Fig.2.HRTEM observations of needle precipitates in AA6061-T6.(a)Lattice image at high magniﬁcation;(b)diffractogram(numerical Fourier transform)of the micrograph showing diffraction spots(arrows)arising from the precipitate in addition to the square lattice of the aluminium fcc phase along[001].appears that f v=3%is not representative of the real precipitation state because it is too dense.The volume fraction of1.6%is obvi-ously closer to the volume fraction observed by TEM.The same type of study carried out for the two other investigated states givesa similar volume fraction.3.3.Mechanical characterizationAs indicated previously,three parameters have been investi-gated.Theﬁrst one is the maximum temperature reached at a given heating rate(r=15K/s).The second one is the heating rate for a given maximum temperature(T=400◦C).The third one is the dwell time at T=560◦C.3.3.1.Inﬂuence of the maximum temperature reached at constant heating rateTheﬁrst mechanical study carried out at room temperature deals with the inﬂuence of the maximum temperature reached at a given heating rate on the mechanical properties of the AA6061-T6.The maximum temperatures are T=200,300,400,450,500and 560◦C at a heating rate of r=15K/s.The variations of temperature with time for these various thermal loadings are shown in Fig.5. The tensile tests are then conducted at room temperature and the corresponding true stress—logarithmic strain curves are shown in Fig.6.The curves obtained for the heated specimens are compared with the curve obtained for the T6temper without thermal loading (black continuous line).It is found that the thermal loading con-siderably inﬂuences the mechanical properties of the specimens except for a maximum temperature of200◦C for which the curve (not shown in Fig.6)is exactly the same as that of the T6sample. Indeed,the yield stress Rp0.2decreases from278MPa at T=300◦C to 70MPa at T=500◦C.Increasing the temperature further to560◦C, however,does not change the yield stress.Fig.7illustrates this 75%decrease of the yield stress when the maximum temperature is increased from300to500◦C.The measured values are compared to values from the literature[21]for which the maximumtemper-parison of three precipitation states.(a)T6temper;(b)after heating up to300◦C at15K s−1;(c)after heating up to400◦C at15K s−1.All micrographs were taken along a 100 zone-axis of the aluminium matrix.2722 D.Maisonnette et al./Materials Science and Engineering A528 (2011) 2718–2724Fig.4.Modeling of the precipitate distribution for a reached temperature T =300◦C with r avg =2.6nm and L avg =25nm assuming volume fractions of (a)3%and (c)1.6%and comparison with the real precipitate distribution microstructure observed by TEM (b)displayed at the same scale.The volume fraction of 1.6%is obviously closer toreality.Fig.5.Thermal loadings used for the study of the inﬂuence of the reached temper-ature.Fig.6.True stress—logarithmic strain curves for temperatures up to 560◦C.ature has been held during 30min.It shows that the yield stress at ambient temperature is strongly dependent on the peak tempera-ture reached during the thermal loading,without a dwell time at the highest temperature,for peak temperature higher than 200◦C.No data without dwell time at the maximum temperature have been found in the literature.The Young modulus has been also measured for each specimen.It has been measured ﬁrstly at the origin of the stress–strain curve and then during the elastic unloading.A mean value is then calcu-lated.It decreases from 68.7GPa for the T6temper to 65.0GPa for the specimen heated to 560◦C which represents a 5.4%decrease.3.3.2.Inﬂuence of the heating rateThe second mechanical study investigates the inﬂuence of the heating rate on the mechanical properties of the AA6061-T6.The maximum temperature applied here is T =400◦C and the studied heating rates are:r =0.5,5,15,50,and 200K/s.The tempera-ture variation obtained for r =50K/s shows an overshoot of 8◦C which results in a slight decrease of the measured stress.Simi-larly,the temperature of the specimen heated with a heating rate of r =200K/s did not reach T =400◦C but T =362◦C.Consequently,the measured stress for this specimen would be higher than expected.The tensile tests give the true stress—logarithmic strain curves shown in Fig.8.They show that the yield stress Rp 0.2decreasesFig.7.Yield stress variation versus reached temperature from measurements (with-out temperature holding)and from the literature (with a 30min dwell time).D.Maisonnette et al./Materials Science and Engineering A528 (2011) 2718–27242723Fig.8.True stress—logarithmic strain curves for various heating rates up to200K/s. for every heated specimens compared to the T6temper and the lower the heating rate is,the lower the yield stress of the material is.More precisely Rp0.2decreases from170MPa for a heating rate of r=200K/s to96MPa for a heating rate of r=0.5K/s.These values have not been compared with literature since no data dealing with the inﬂuence of the heating rate has been found.3.3.3.Inﬂuence of holding time at560◦CThe last mechanical study accomplished on the material is con-cerned with the inﬂuence of a holding time at high temperature before doing the tensile test at room temperature.This last study compares the mechanical properties of the AA6061-T6after a heat-ing at T=560◦C with and without a dwell time at this temperature. The temperature T=560◦C has been chosen because it is close to the solvus temperature of the␤phase in the␣phase.The chosen dwell time is t=30min and the heating rate is r=15K/s.The mechanical properties obtained for both cases are strictly identical.This result indicates that the dwell time at T=560◦C does not inﬂuence the mechanical properties measured on the tested specimens.4.Discussion4.1.PrecipitationAccording to literature[5–9,13,14],the precipitates which are normally present in the T6temper of the AA6061alloy are very thin and their density is quite high.They are small needles of␤ (or pre-␤ )type.They are oriented following the three 100 matrix directions.Some authors[6,10,22]have carried out a detailed study of the␤ phase.It appears that the X Mg/X Si atomic ratio is very often close to1as reported in Table1.However,other authors[23]man-aged to measure a X Mg/X Si ratio higher than1for GP zones and co-clusters contained in an aged6061.In addition,the observed precipitates are only partially coherent as for the pre-␤ phase. Based on these results,it can be assumed that the precipitates con-tained in the studied reference material are pre-␤ or␤ phases (although the X Mg/X Si atomic ratio measured here to1.29is slightly higher than1).Otherwise,Andersen et al.[6]measured needle pre-cipitates with a size of about4nm×4nm×50nm for the␤ phase and20nm×20nm×500nm for the␤ phase.Furthermore,Don-nadieu et al.[8]measured the size of the precipitates contained in a 6065-T6alloy.They obtained a mean diameter of2.86nm.By com-paring these values to those presented in Sections3.1and3.2it can be assumed that the precipitates contained in the studied AA6061 after heating at400◦C are composed of the␤ phase.On the con-trary,the precipitates contained in the6061-T6and in the6061 after a heating at300◦C are smaller.Therefore,the precipitates are probably remaining␤ precipitates for the6061alloy after heating at300◦C.In addition to that,large intermetallics are visible in the micro-graphs at low magniﬁcation,as shown in Fig.9.The size of the intermetallics ranges from50to300nm.These intermetallics formed during the elaboration of the material do not contribute to the hardening of the alloy.An energy dispersive X-ray spectrometry analysis(EDX)proved that their composition type is(Fe–Cr–Mn–Si) and not(Al–Mg–Si)as for hardening precipitates.The structure of these intermetallics was not investigated further.However,it is important to note that the intermetallics do contain silicon,so that the corresponding quantity will not be available for hardening precipitation.4.2.Mechanical propertiesFig.6showed that the behavior of the material after heating at500◦C is strictly identical to the behavior of the material after heating at560◦C.Thus,it can be assumed that the microstructure is the same in both cases.Furthermore,a tensile test carried out on a specimen heated to560◦C during30min gives exactly the same behavior.This behavior corresponds to the O temper.It is commonly accepted that a long holding time at T=560◦C(solvus temperature of the␤phase in the␣phase)is required to dis-solve the parison of the true stress—logarithmic strain curves obtained with and without dwell time shows that the mechanical properties are identical.This means that the dwell time at T=560◦C does not change the mechanical properties.The microstructure is therefore identical corresponding to the annealed state(or O temper)for which no precipitate is present in the mate-rial.This last result shows that for the heating rate and for the specimens used in this study,it is not necessary to apply a dwell time to reach the O temper.This conclusion is probably not valid in the case of a large structure since the peak temperature at each point within the material would depend on its distance from the closest surface.Another result of this investigation is that the heat-ing rate has an inﬂuence on the mechanical properties.By using a higher heating rate,the O temper could not be obtained without a dwell time.The hardening is due to the precipitates contained within the material.They hinder dislocation glide.For a given volume fraction, hardening is most effective if the precipitates are small(and there-fore more numerous).These small precipitates have been observed by TEM for the T6temper.This microstructure leads to more favor-able mechanical properties than the other investigated states.The behavior observed here is quite close to the one observed by Zain-ul-Abdein et al.[24]on a6056-T4.Then,the microstructure of the specimen heated to300◦C seems to be close to the one observed for the T6temper,which explains the small difference of mechanical properties.If the maximum temperature is further increased,the yield stress Rp0.2decreases signiﬁcantly as shown in Fig.7.The TEM observations show that this decrease is due to a strongly enhanced growth of the precipitates.The volume fraction of the precipitates remains identical so that the precipitate number is decreased.This results in a sharp decrease of the mechanical properties,as high-lighted by the tensile tests.Concerning the study of the inﬂuence of the heating rate,no microstructural observations have been carried out.However,Fig.8 shows a decrease of the mechanical properties for every thermal loading up to400◦C compared to the mechanical properties of the T6temper.This means that the material has encountered a microstructural change for every investigated heating rate.If the heating rate is very low,the microstructural changes as dissolution and growth of precipitates,have more time to occur.Consequently, less precipitates are present(for a constant volume fraction)and the mechanical properties are lower.The Young modulus has been measured and it has been shown that it decreases slightly compared to the T6state when。

土木工程类SCI期刊

24 INTERNA TIONAL JOURNAL OF SOLIDS AND STRUCTURESBiweeklyISSN: 0020-7683PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEV ARD, LANGFORD LANE, KIDLINGTON, OXFORD21 INTERNA TIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS INGEOMECHANICSMonthlyISSN: 0363-9061JOHN WILEY& SONS LTD, THE A TRIUM, SOUTHERN GA TE, CHICHESTER, ENGLAND, W SUSSEX, PO19 8SQ17 FINITE ELEMENTS IN ANALYSIS AND DESIGNMonthlyISSN: 0168-874XELSEVIER SCIENCE BV, PO BOX 211, AMSTERDAM, NETHERLANDS, 1000 AE11 COMPUTERS & STRUCTURESBiweeklyISSN: 0045-7949PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEV ARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND, OX5 1GB10 COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERINGSemimonthlyISSN: 0045-7825ELSEVIER SCIENCE SA, PO BOX 564, LAUSANNE, SWITZERLAND, 10019 CANADIAN JOURNAL OF CIVIL ENGINEERINGBimonthlyISSN: 0315-1468NA TL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS, BUILDING M 55, OTTA WA, CANADA, ON, K1A 0R68 CANADIAN GEOTECHNICAL JOURNALBimonthlyISSN: 0008-3674NA TL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS, BUILDING M 55, OTTA WA, CANADA, ON, K1A 0R6SCI收录期刊——土木建筑工程学科万跃华2009年2月12日SCI和A&HCI分别收录建筑学科期刊，SCI主要收录土木建筑工程期刊，A&HCI收录建筑设计期刊。

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Thermally Induced Solid-State Phase Transition of TIPS Pentacene Crystals Jihua Chen1, John Anthony4, and David C. Martin1,2,3* 1Macromolecular Science and Engineering Center

2Department of Materials Science and Engineering

3Department of Biomedical Engineering

The University of Michigan

4Department of Chemistry

The University of Kentucky

*To whom correspondence should be addressed. Email: milty@umich.edu (Submit to Journal of Physical Chemistry B) ABSTRACT Bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) is a functionalized pentacene derivative designed to enhance both the solution solubility and solid state packing of pentacene. In this paper, we report our observations of a solid-state phase transition in TIPS pentacene crystals upon heating or cooling. Evidence from differential scanning calorimetry (DSC), hot-stage optical microscopy, as well as high temperature X-ray and electron diffraction are presented. A reasonable match with experimental data is obtained with molecular modeling. Our results reveal that the transition is associated with a conformational reorganization of the TIPS side groups, accompanied by a slight decrease in the acene-to-acene spacing and a shift of the overlap between the neighboring pentacene units. The observed cracking should be avoided or minimized in TIPS pentacene-based thin film transistors in order to maintain their relatively high charge carrier mobility.

Introduction With their enormous variability and potentially low-cost fabrication, organic electronic materials have attracted significant recent commercial and scientific interest. In particular, pentacene has been extensively studied as an organic molecular semiconductor in various thin film applications 1-3. However, pentacene is not soluble in any convenient organic solvents, which rules out its use in solution processing. In addition, pentacene molecules are known to adopt a herringbone structure in the crystal, so that their lateral π-π overlap interactions are not optimized. Although pentacene, with its measured mobility values as high as 1.5 Cm2/V.s 4, is currently among the organic materials with highest charge carrier mobilities known, it is believed that there still could be improvements in pentacene’s mobility if its π-π interactions could be enhanced.

Bis-(triisopropylsilylethynyl) pentacene (TIPS pentacene) was synthesized to address precisely those two issues (Figure 1). On one hand, the TIPS side groups makes TIPS pentacene soluble in common organic solvents; on the other hand, these bulky groups also help to disrupt the face-to-edge herringbone pattern and to form a regular columnar stacking between acene planes 5; 6. The effects of temperature, pressure and iodine doping, as well as the crystallographic anisotropy on the electrical resistivity of TIPS pentacene single crystals have been examined previously 7. In addition, Extended Huckel Theory (EHT) calculations of band electronic structure 8, thin film transistor characteristics 9, and photoconductivity 10 have been reported for this organic semiconductor, and have been compared to either unmodified pentacene or pentacene derivatives with other side groups (such as trimethylsilylethynyl TMS). Recent ultra-fast photoconductivity experiments suggest that in TIPS pentacene thin films, there is a band-like charge carrier transport at sub-picosecond time scales 11.

The thermal properties of organic molecular semiconductors could be critical for thin film applications, not only because the elevated substrate temperature sometimes adopted in fabrication may form crystalline grains with larger domain sizes, but also because of the end-use requirements in different applications. In this paper, we report on a thermally induced solid-state phase transition in crystalline TIPS pentacene thin films. This phase transition leads to the formation of crystallographically well-defined cracks throughout the TIPS-pentacene single crystals. This phase transition should be avoided or at least minimized in fabrication and application of TIPS pentacene-based thin film transistors in order to maintain their relatively high charge carrier mobility.

Experiments: Materials. The synthesis of TIPS pentacene was published elsewhere 6. The TIPS pentacene crystals are dark blue and adopt needle- or platelet- shapes. According to selected area electron diffraction results, many needle-shaped crystals had the long axis along (120) planes, which was about 30 degree off the “a” axis.