High-temperature mechanical properties and deformation behavior of high Nb containing TiAl alloy
高性能热塑性材料介绍
SEMI-CRYSTALLINE COMMODITY PLASTICS
Key Characteristics: Low Cost Low Temperature Resistance Low Strength Excellent Chemical Resistance Low Coefficient of Friction Near Zero Moisture Absorption Very Good Electrical Properties Good Toughness Materials: Polyethylene Polypropylene Polymetnylpentene(TPX)
Polyimide (PI)聚酰亚
Limitations 局限性
Low physical properties 物理性能低 Poor in high temp applications 不耐高温 Cost 成本
Polyimide (PI)聚酰亚
Applications 适用于
Aerospace 航空 Semiconductor 半導体 Electrical/electronic 電器/電子 Transportation 運輸 Off highway equipment 非公路設施 Pump and valve 水泵及閥門 Hydraulics 液壓机 Automotive 汽車 Textile 紡織品 Clean rooms 房間清洁
成本非常高
Polyamide-imide (PAI)聚酰胺-酰亚胺
Applications 适用于
Computer wafer handling units 電腦晶片處理零件 Bearings 軸承 Compressor vanes 气壓机葉片 Lantern rings 投影儀套環 Pump housings 水泵機架 Hydraulic components 液壓机組件 Glass handling parts 玻璃處理零件
Microstructures and properties of high-entropy
Microstructures and properties of high-entropyalloysYong Zhang a ,⇑,Ting Ting Zuo a ,Zhi Tang b ,Michael C.Gao c ,d ,Karin A.Dahmen e ,Peter K.Liaw b ,Zhao Ping Lu aa State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,Chinab Department of Materials Science and Engineering,The University of Tennessee,Knoxville,TN 37996,USAc National Energy Technology Laboratory,1450Queen Ave SW,Albany,OR 97321,USAd URS Corporation,PO Box 1959,Albany,OR 97321-2198,USAe Department of Physics,University of Illinois at Urbana-Champaign,1110West Green Street,Urbana,IL 61801-3080,USA a r t i c l e i n f o Article history:Received 26September 2013Accepted 8October 2013Available online 1November 2013a b s t r a c tThis paper reviews the recent research and development of high-entropy alloys (HEAs).HEAs are loosely defined as solid solutionalloys that contain more than five principal elements in equal ornear equal atomic percent (at.%).The concept of high entropyintroduces a new path of developing advanced materials withunique properties,which cannot be achieved by the conventionalmicro-alloying approach based on only one dominant element.Up to date,many HEAs with promising properties have beenreported, e.g.,high wear-resistant HEAs,Co 1.5CrFeNi 1.5Ti andAl 0.2Co 1.5CrFeNi 1.5Ti alloys;high-strength body-centered-cubic(BCC)AlCoCrFeNi HEAs at room temperature,and NbMoTaV HEAat elevated temperatures.Furthermore,the general corrosion resis-tance of the Cu 0.5NiAlCoCrFeSi HEA is much better than that of theconventional 304-stainless steel.This paper first reviews HEA for-mation in relation to thermodynamics,kinetics,and processing.Physical,magnetic,chemical,and mechanical properties are thendiscussed.Great details are provided on the plastic deformation,fracture,and magnetization from the perspectives of cracklingnoise and Barkhausen noise measurements,and the analysis of ser-rations on stress–strain curves at specific strain rates or testingtemperatures,as well as the serrations of the magnetizationhysteresis loops.The comparison between conventional andhigh-entropy bulk metallic glasses is analyzed from the viewpointsof eutectic composition,dense atomic packing,and entropy of 0079-6425/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.pmatsci.2013.10.001⇑Corresponding author.Tel.:+8601062333073;fax:+8601062333447.E-mail address:*****************.cn (Y.Zhang).2Y.Zhang et al./Progress in Materials Science61(2014)1–93mixing.Glass forming ability and plastic properties of high-entropy bulk metallic glasses are also discussed.Modeling tech-niques applicable to HEAs are introduced and discussed,such asab initio molecular dynamics simulations and CALPHAD modeling.Finally,future developments and potential new research directionsfor HEAs are proposed.Ó2013Elsevier Ltd.All rights reserved. Contents1.Introduction (3)1.1.Four core effects (4)1.1.1.High-entropy effect (4)1.1.2.Sluggish diffusion effect (5)1.1.3.Severe lattice-distortion effect (6)1.1.4.Cocktail effect (7)1.2.Key research topics (9)1.2.1.Mechanical properties compared with other alloys (10)1.2.2.Underlying mechanisms for mechanical properties (11)1.2.3.Alloy design and preparation for HEAs (11)1.2.4.Theoretical simulations for HEAs (12)2.Thermodynamics (12)2.1.Entropy (13)2.2.Thermodynamic considerations of phase formation (15)2.3.Microstructures of HEAs (18)3.Kinetics and alloy preparation (23)3.1.Preparation from the liquid state (24)3.2.Preparation from the solid state (29)3.3.Preparation from the gas state (30)3.4.Electrochemical preparation (34)4.Properties (34)4.1.Mechanical behavior (34)4.1.1.Mechanical behavior at room temperature (35)4.1.2.Mechanical behavior at elevated temperatures (38)4.1.3.Mechanical behavior at cryogenic temperatures (45)4.1.4.Fatigue behavior (46)4.1.5.Wear behavior (48)4.1.6.Summary (49)4.2.Physical behavior (50)4.3.Biomedical,chemical and other behaviors (53)5.Serrations and deformation mechanisms (55)5.1.Serrations for HEAs (56)5.2.Barkhausen noise for HEAs (58)5.3.Modeling the Serrations of HEAs (61)5.4.Deformation mechanisms for HEAs (66)6.Glass formation in high-entropy alloys (67)6.1.High-entropy effects on glass formation (67)6.1.1.The best glass former is located at the eutectic compositions (67)6.1.2.The best glass former is the composition with dense atomic packing (67)6.1.3.The best glass former has high entropy of mixing (67)6.2.GFA for HEAs (68)6.3.Properties of high-entropy BMGs (70)7.Modeling and simulations (72)7.1.DFT calculations (73)7.2.AIMD simulations (75)7.3.CALPHAD modeling (80)8.Future development and research (81)Y.Zhang et al./Progress in Materials Science61(2014)1–9338.1.Fundamental understanding of HEAs (82)8.2.Processing and characterization of HEAs (83)8.3.Applications of HEAs (83)9.Summary (84)Disclaimer (85)Acknowledgements (85)References (85)1.IntroductionRecently,high-entropy alloys(HEAs)have attracted increasing attentions because of their unique compositions,microstructures,and adjustable properties[1–31].They are loosely defined as solid solution alloys that contain more thanfive principal elements in equal or near equal atomic percent (at.%)[32].Normally,the atomic fraction of each component is greater than5at.%.The multi-compo-nent equi-molar alloys should be located at the center of a multi-component phase diagram,and their configuration entropy of mixing reaches its maximum(R Ln N;R is the gas constant and N the number of component in the system)for a solution phase.These alloys are defined as HEAs by Yeh et al.[2], and named by Cantor et al.[1,33]as multi-component alloys.Both refer to the same concept.There are also some other names,such as multi-principal-elements alloys,equi-molar alloys,equi-atomic ratio alloys,substitutional alloys,and multi-component alloys.Cantor et al.[1,33]pointed out that a conventional alloy development strategy leads to an enor-mous amount of knowledge about alloys based on one or two components,but little or no knowledge about alloys containing several main components in near-equal proportions.Theoretical and experi-mental works on the occurrence,structure,and properties of crystalline phases have been restricted to alloys based on one or two main components.Thus,the information and understanding are highly developed on alloys close to the corners and edges of a multi-component phase diagram,with much less knowledge about alloys located at the center of the phase diagram,as shown schematically for ternary and quaternary alloy systems in Fig.1.1.This imbalance is significant for ternary alloys but becomes rapidly much more pronounced as the number of components increases.For most quater-nary and other higher-order systems,information about alloys at the center of the phase diagram is virtually nonexistent except those HEA systems that have been reported very recently.In the1990s,researchers began to explore for metallic alloys with super-high glass-forming ability (GFA).Greer[29]proposed a confusion principle,which states that the more elements involved,the lower the chance that the alloy can select viable crystal structures,and thus the greater the chanceand quaternary alloy systems,showing regions of the phase diagram thatand relatively less well known(white)near the center[33].4Y.Zhang et al./Progress in Materials Science61(2014)1–93solid-solutions even though the cooling rate is very high,e.g.,alloys of CuCoNiCrAlFeTiV,FeCrMnNiCo, CoCrFeNiCu,AlCoCrFeNi,NbMoTaWV,etc.[1,2,12–14].The yield strength of the body-centered cubic(BCC)HEAs can be rather high[12],usually compa-rable to BMGs[12].Moreover,the high strength can be kept up to800K or higher for some HEAs based on3d transition metals[14].In contrast,BMGs can only keep their high strength below their glass-transition temperature.1.1.Four core effectsBeing different from the conventional alloys,compositions in HEAs are complex due to the equi-molar concentration of each component.Yeh[37]summarized mainly four core effects for HEAs,that is:(1)Thermodynamics:high-entropy effects;(2)Kinetics:sluggish diffusion;(3)Structures:severe lattice distortion;and(4)Properties:cocktail effects.We will discuss these four core effects separately.1.1.1.High-entropy effectThe high-entropy effects,which tend to stabilize the high-entropy phases,e.g.,solid-solution phases,werefirstly proposed by Yeh[9].The effects were very counterintuitive because it was ex-pected that intermetallic compound phases may form for those equi-or near equi-atomic alloy com-positions which are located at the center of the phase diagrams(for example,a monoclinic compound AlCeCo forms in the center of Al–Ce–Co system[38]).According to the Gibbs phase rule,the number of phases(P)in a given alloy at constant pressure in equilibrium condition is:P¼Cþ1ÀFð1-1Þwhere C is the number of components and F is the maximum number of thermodynamic degrees of freedom in the system.In the case of a6-component system at given pressure,one might expect a maximum of7equilibrium phases at an invariant reaction.However,to our surprise,HEAs form so-lid-solution phases rather than intermetallic phases[1,2,4,17].This is not to say that all multi-compo-nents in equal molar ratio will form solid solution phases at the center of the phase diagram.In fact, only carefully chosen compositions that satisfy the HEA-formation criteria will form solid solutions instead of intermetallic compounds.The solid-solution phase,according to the classical physical-metallurgy theory,is also called a ter-minal solid solution.The solid-solution phase is based on one element,which is called the solvent,and contains other minor elements,which are called the solutes.In HEAs,it is very difficult to differentiate the solvent from the solute because of their equi-molar portions.Many researchers reported that the multi-principal-element alloys can only form simple phases of body-centered-cubic(BCC)or face-cen-tered-cubic(FCC)solid solutions,and the number of phases formed is much fewer than the maximum number of phases that the Gibbs phase rule allows[9,23].This feature also indicates that the high en-tropy of the alloys tends to expand the solution limits between the elements,which may further con-firm the high-entropy effects.The high-entropy effect is mainly used to explain the multi-principal-element solid solution. According to the maximum entropy production principle(MEPP)[39],high entropy tends to stabilize the high-entropy phases,i.e.,solid-solution phases,rather than intermetallic phases.Intermetallics are usually ordered phases with lower configurational entropy.For stoichiometric intermetallic com-pounds,their configurational entropy is zero.Whether a HEA of single solid solution phase is in its equilibrium has been questioned in the sci-entific community.There have been accumulated evidences to show that the high entropy of mixing truly extends the solubility limits of solid solution.For example,Lucas et al.[40]recently reported ab-sence of long-range chemical ordering in equi-molar FeCoCrNi alloy that forms a disordered FCC struc-ture.On the other hand,it was reported that some equi-atomic compositions such as AlCoCrCuFeNi contain several phases of different compositions when cooling slowly from the melt[15],and thus it is controversial whether they can be still classified as HEA.The empirical rules in guiding HEA for-mation are addressed in Section2,which includes atomic size difference and heat of mixing.Y.Zhang et al./Progress in Materials Science61(2014)1–935 1.1.2.Sluggish diffusion effectThe sluggish diffusion effect here is compared with that of the conventional alloys rather than the bulk-glass-forming alloys.Recently,Yeh[9]studied the vacancy formation and the composition par-tition in HEAs,and compared the diffusion coefficients for the elements in pure metals,stainless steels, and HEAs,and found that the order of diffusion rates in the three types of alloy systems is shown be-low:Microstructures of an as-cast CuCoNiCrAlFe alloy.(A)SEM micrograph of an etched alloy withBCC and ordered BCC phases)and interdendrite(an FCC phase)structures.(B)TEMplate,70-nm wide,a disordered BCC phase(A2),lattice constant,2.89A;(B-b)aphase(B2),lattice constant,2.89A;(B-c)nanoprecipitation in a spinodal plate,7nm(B-d)nanoprecipitation in an interspinodal plate,3nm in diameter,a disorderedarea diffraction(SAD)patterns of B,Ba,and Bb with zone axes of BCC[01[011],respectively[2].illustration of intrinsic lattice distortion effects on Bragg diffraction:(a)perfect latticewith solid solutions of different-sized atoms,which are expected to randomly distribute statistical average probability of occupancy;(c)temperature and distortion effectsY.Zhang et al./Progress in Materials Science61(2014)1–937 the intensities further drop beyond the thermal effect with increasing the number of constituent prin-cipal elements.An intrinsic lattice distortion effect caused by the addition of multi-principal elements with different atomic sizes is expected for the anomalous decrease in the XRD intensities.The math-ematical treatment of this distortion effect for the modification of the XRD structure factor is formu-lated to be similar to that of the thermal effect,as shown in Fig.1.3[41].The larger roughness of the atomic planes makes the intensity of the XRD for HEAs much lower than that for the single-element solid.The severe lattice distortion is also used to explain the high strength of HEAs,especially the BCC-structured HEAs[4,12,23].The severe lattice-distortion effect is also related to the tensile brittle-ness and the slower kinetics of HEAs[2,9,11].However,the authors also noticed that single-phase FCC-structured HEAs have very low strength[7],which certainly cannot be explained by the severe lattice distortion argument.Fundamental studies in quantification of lattice distortion of HEAs are needed.1.1.4.Cocktail effectThe cocktail-party effect was usually used as a term in the acousticsfield,which have been used to describe the ability to focus one’s listening attention on a single talker among a mixture of conversa-tions and background noises,ignoring other conversations.For metallic alloys,the effect indicates that the unexpected properties can be obtained after mixing many elements,which could not be obtained from any one independent element.The cocktail effect for metallic alloys wasfirst mentioned by Ranganathan[42],which has been subsequently confirmed in the mechanical and physical properties [12,13,15,18,35,43].The cocktail effect implies that the alloy properties can be greatly adjusted by the composition change and alloying,as shown in Fig.1.4,which indicates that the hardness of HEAs can be dramat-ically changed by adjusting the Al content in the CoCrCuNiAl x HEAs.With the increase of the Al con-lattice constants of a CuCoNiCrAl x Fe alloy system with different x values:(A)hardnessconstants of an FCC phase,(C)lattice constants of a BCC phase[2].CoCrCuFeNiAl x [15,45].Cu forms isomorphous solid solution with Ni but it is insoluble in Co,Cr and Fe;it dissolves about 20at.%Al but also forms various stable intermetallic compounds with Al.Fig.1.6exhibits the hardness of some reported HEAs in the descending order with stainless steels as benchmark.The MoTiVFeNiZrCoCr alloy has a very high value of hardness of over 800HV while CoCrFeNiCu is very soft with a value of less than 200HV.Fig.1.7compares the specific strength,whichyield strength over the density of the materials,and the density among alloys,polymers and foam materials [5].We can see that HEAs have densities high values of specific strength (yield strength/density).This is partially HEAs usually contain mainly the late transitional elements whose lightweight HEAs have much more potential because lightweight density of the resultant alloys will be lowered significantly.Fig.1.8strength of HEAs vs.Young’s modulus compared with conventional alloys.highest specific strength and their Young’s modulus can be varied CoNiCrAl x Fe alloy system with different x values,the Cu-free alloy has lower hardness .range of hardness for HEAs,compared with 17–4PH stainless steel,Hastelloy,andYield strength,r y,vs.density,q.HEAs(dark dashed circle)compared with other materials,particularly structural Grey dashed contours(arrow indication)label the specific strength,r y/q,from low(right bottom)to high(left top).among the materials with highest strength and specific strength[5].Specific-yield strength vs.Young’s modulus:HEAs compared with other materials,particularly structural alloys.among the materials with highest specific strength and with a wide range of Young’s modulus[5].range.This observation may indicate that the modulus of HEAs can be more easily adjusted than con-ventional alloys.In addition to the high specific strength,other properties such as high hydrogen stor-age property are also reported[46].1.2.Key research topicsTo understand the fundamentals of HEAs is a challenge to the scientists in materials science and relatedfields because of lack of thermodynamic and kinetic data for multi-component systems in the center of phase diagrams.The phase diagrams are usually available only for the binary and ternary alloys.For HEAs,no complete phase diagrams are currently available to directly assist designing the10Y.Zhang et al./Progress in Materials Science61(2014)1–93alloy with desirable micro-and nanostructures.Recently,Yang and Zhang[28]proposed the X param-eter to design the solid-solution phase HEAs,which should be used combing with the parameter of atomic-size difference.This strategy may provide a starting point prior to actual experiments.The plastic deformation and fracture mechanisms of HEAs are also new because the high-entropy solid solutions contain high contents of multi-principal elements.In single principal-element alloys,dislo-cations dominate the plastic behavior.However,how dislocations interact with highly-disordered crystal lattices and/or chemical disordering/ordering will be an important factor responsible for plastic properties of HEAs.Interactions between the other crystal defects,such as twinning and stacking faults,with chemical/crystal disordering/ordering in HEAs will be important as well.1.2.1.Mechanical properties compared with other alloysFor conventional alloys that contain a single principal element,the main mechanical behavior is dictated by the dominant element.The other minor alloying elements are used to enhance some spe-cial properties.For example,in the low-carbon ferritic steels[47–59],the main mechanical properties are from the BCC Fe.Carbon,which is an interstitial solute element,is used for solid-solution strength-ened steels,and also to enhance the martensite-quenching ability which is the phase-transformation strengthening.The main properties of steels are still from Fe.For aluminum alloys[60]and titanium alloys[61],their properties are mainly related to the dominance of the elemental aluminum and tita-nium,respectively.Intermetallic compounds are usually based on two elements,e.g.,Ti–Al,Fe3Al,and Fe3Si.Interme-tallic compounds are typically ordered phases and some may have strict compositional range.The Burgers vectors of the ordered phases are too large for the dislocations to move,which is the main reason why intermetallic phases are usually brittle.However,there are many successful case studies to improve the ductility of intermetallic compound by micro-alloying,e.g.,micro-alloying of B in Ni3Al [62],and micro-alloying of Cr in Fe3Al[63,64].Amorphous metals usually contain at least three elements although binary metallic glasses are also reported,and higher GFA can be obtained with addition of more elements,e.g.,ZrTiCuNiBe(Vit-1), PdNiCuP,LaAlNiCu,and CuZrAlY alloys[65–69].Amorphous metals usually exhibit ultrahigh yield strength,because they do not contain conventional any weakening factors,such as dislocations and grain boundaries,and their yield strengths are usually three tofive times of their corresponding crys-talline counterpart alloys.There are several models that are proposed to explain the plastic deforma-tion of the amorphous metal,including the free volume[70],a shear-transformation-zone(STZ)[71], more recently a tension-transition zone(TTZ)[72],and the atomic-level stress[73,74].The micro-mechanisms of the plastic deformation of amorphous metals are usually by forming shear bands, which is still an active research area till today.However,the high strength of amorphous alloys can be sustained only below the glass-transition temperature(T g).At temperatures immediately above T g,the amorphous metals will transit to be viscous liquids[68]and will crystallize at temperatures above thefirst crystallization onset temperature.This trend may limit the high-temperature applica-tions of amorphous metals.The glass forming alloys often are chemically located close to the eutectic composition,which further facilitates the formation of the amorphous metal–matrix composite.The development of the amorphous metal–matrix composite can enhance the room-temperature plastic-ity of amorphous metals,and extend application temperatures[75–78].For HEAs,their properties can be different from any of the constituent elements.The structure types are the dominant factor for controlling the strength or hardness of HEAs[5,12,13].The BCC-structured HEAs usually have very high yield strengths and limited plasticity,while the FCC-structured HEAs have low yield strength and high plasticity.The mixture of BCC+FCC is expected to possess balanced mechanical properties,e.g.,both high strength and good ductility.Recent studies show that the microstructures of certain‘‘HEAs’’can be very complicated since they often undergo the spinodal decomposition,and ordered,and disordered phase precipitates at lower temperatures. Solution-strengthening mechanisms for HEAs would be much different from conventional alloys. HEAs usually have high melting points,and the high yield strength can usually be sustained to ultrahigh temperatures,which is shown in Fig.1.9for refractory metal HEAs.The strength of HEAs are sometimes better than those of conventional superalloys[14].1.2.2.Underlying mechanisms for mechanical propertiesMechanical properties include the Young’s modulus,yield strength,plastic elongation,fracture toughness,and fatigue properties.For the conventional one-element principal alloys,the Young’s modulus is mainly controlled by the dominant element,e.g.,the Young’s modulus of Fe-based alloys is about 200GPa,that of Ti-based alloys is approximately 110GPa,and that of Al-based alloys is about 75GPa,as shown in Fig.1.8.In contrast,for HEAs,the modulus can be very different from any of the constituent elements in the alloys [79],and the moduli of HEAs are scattered in a wide range,as shown in Fig.1.8.Wang et al.[79]reported that the Young’s modulus of the CoCrFeNiCuAl 0.5HEA is about 24.5GPa,which is much lower than the modulus of any of the constituent elements in the alloy.It is even lower than the Young’s modulus of pure Al,about 69GPa [80].On the other hand,this value needs to be verified using other methods including impulse excitation of vibration.It has been reported that the FCC-structured HEAs exhibit low strength and high plasticity [13],while the BCC-structured HEAs show high strength and low plasticity at room temperature [12].Thus,the structure types are the dominant factor for controlling the strength or hardness of HEAs.For the fracture toughness of the HEAs,there is no report up to date.1.2.3.Alloy design and preparation for HEAsIt has been verified that not all the alloys with five-principal elements and with equi-atomic ratio compositions can form HEA solid solutions.Only carefully chosen compositions can form FCC and BCC solid solutions.Till today there is no report on hexagonal close-packed (HCP)-structured HEAs.One reason is probably due to the fact that a HCP structure is often the stable structure at low tempera-tures for pure elements (applicable)in the periodic table,and that it may transform to either BCC or FCC at high temperatures.Most of the HEA solid solutions are identified by trial-and-error exper-iments because there is no phase diagram on quaternary and higher systems.Hence,the trial-and er-ror approach is the main way to develop high-performance HEAs.However,some parameters have been proposed to predict the phase formation of HEAs [17,22,28]in analogy to the Hume-Rothery rule for conventional solid solution.The fundamental thermodynamic equation states:G ¼H ÀTS ð1-2Þwhere H is the enthalpy,S is the entropy,G is the Gibbs free energy,and T is the absolute temperature.From Eq.(1-2),the TS term will become significant at high temperatures.Hence,preparing HEAs from the liquid and gas would provide different kinds of information.These techniques may includesput-Temperature dependence of NbMoTaW,VNbMoTaW,Inconel 718,and Haynes 230tering,laser cladding,plasma coating,and arc melting,which will be discussed in detail in the next chapter.For the atomic-level structures of HEAs,the neutron and synchrotron diffraction methods are useful to detect ordering parameters,long-range order,and short-range ordering[81].1.2.4.Theoretical simulations for HEAsFor HEAs,entropy effects are the core to their formation and properties.Some immediate questions are:(1)How can we accurately predict the total entropy of HEA phase?(2)How can we predict the phasefield of a HEA phase as a function of compositions and temperatures?(3)What are the proper modeling and experimental methods to study HEAs?To address the phase-stability issue,thermody-namic modeling is necessary as thefirst step to understand the fundamental of HEAs.The typical mod-eling techniques to address thermodynamics include the calculation of phase diagram(CALPHAD) modeling,first-principle calculations,molecular-dynamics(MD)simulations,and Monte Carlo simulations.Kao et al.[82]using MD to study the structure of HEAs,and their modeling efforts can well explain the liquid-like structure of HEAs,as shown in Fig.1.10.Grosso et al.[83]studied refractory HEAs using atomistic modeling,clarified the role of each element and their interactions,and concluded that4-and 5-elements alloys are possible to quantify the transition to a high-entropy regime characterized by the formation of a continuous solid solution.2.Thermodynamicsof a liquid-like atomic-packing structure using multiple elementsthird,fourth,andfifth shells,respectively,but the second and third shellsdifference and thus the largefluctuation in occupation of different atoms.2.1.EntropyEntropy is a thermodynamic property that can be used to determine the energy available for the useful work in a thermodynamic process,such as in energy-conversion devices,engines,or machines. The following equation is the definition of entropy:dS¼D QTð2-1Þwhere S is the entropy,Q is the heatflow,and T is the absolute temperature.Thermodynamic entropy has the dimension of energy divided by temperature,and a unit of Joules per Kelvin(J/K)in the Inter-national System of Units.The statistical-mechanics definition of entropy was developed by Ludwig Boltzmann in the1870s [85]and by analyzing the statistical behavior of the microscopic components of the system[86].Boltz-mann’s hypothesis states that the entropy of a system is linearly related to the logarithm of the fre-quency of occurrence of a macro-state or,more precisely,the number,W,of possible micro-states corresponding to the macroscopic state of a system:Fig.2.1.Illustration of the D S mix for ternary alloy system with the composition change[17].。
JMatPro计算原理探讨
Modelling properties and behaviour: JMatPro 材料性能模拟： JMatPro
3.1 Thermodynamic Calculations: Background
相转变（TTT/CCT相图）
1200
Temperature (
1000
RR2071
Calculated TTT diagram for the single crystal alloy RR2071 with experimental results of Rae at al. superimposed RR2071合金计算的TTT曲线与Rae at al.的实验结果的比较
可考虑两种强化机制
• Solid solution strengthening.
固溶强化
• Particle strengthening.
第二相粒子强化
3.4.1 Mechanical Properties (Precipitation Hardening) 机械性能（析出强化）
The yield strength of an alloy hardened by γ’ particles can be given by the equation below for small particles
80
90
100
Particle Diameter (nm)
Exp. 0.2% Proof Stress (MPa)
3.4.4 Ageing Response of a Ni-based Superalloy (combining coarsening and pptn hardening) 镍基超合金时效效应（综合晶粒长大和析出强化）
高温对含氢DLC_涂层的微观结构及力学性能的影响
表面技术第53卷第5期高温对含氢DLC涂层的微观结构及力学性能的影响贾伟飞1，梁灿棉2，胡锋1,2*（1.武汉科技大学 高性能钢铁材料及其应用省部共建协同创新中心，武汉 430081；2.广东星联精密机械有限公司，广东 佛山 528251）摘要：目的针对含氢DLC涂层热稳定性很差的问题，探究高温下含氢DLC涂层的微观组织变化特征，以及高温对其力学性能的影响。
方法采用等离子体强化化学气相沉积（Plasma Enhanced Chemical Vapor Deposition, PECVD）在S136模具不锈钢表面沉积以Si为过渡层的含氢DLC复合涂层，利用光学显微镜、扫描电镜、拉曼光谱、X射线电子衍射仪、三维轮廓仪研究DLC涂层的微观结构，采用划痕测试仪、往复式摩擦磨损试验机、纳米压痕仪研究DLC涂层的力学性能，并通过LAMMPS软件，利用液相淬火法建立含氢DLC模型，模拟分析经高温处理后涂层的组织变化特征和纳米压痕行为。
结果在400 ℃、2 h的退火条件下，拉曼谱峰强度I D/I G由未退火的0.7增至1.5，涂层发生了石墨化转变，同时基线斜率下降，H元素析出；XPS结果表明，在此条件下涂层中sp2杂化组织相对增加，氧元素增多，涂层粗糙度增大；在600 ℃、2 h退火条件下，DLC发生了严重氧化，LAMMPS模拟结果表明，在400 ℃高温下涂层的分子键长变短，表明sp3杂化组织在高温下吸收能量，并向sp2杂化转变。
纳米压痕模拟结果显示，在400 ℃下退火后，涂层的硬度下降。
结论在400 ℃下退火处理后，涂层中的H元素释放，涂层内应力减小，保证了涂层的强度；在600 ℃退火条件下，过渡层的Si和DLC在高温下形成了C—Si键，使得DLC薄膜部分被保留；LAMMPS 模拟结果表明，在高温下涂层发生了石墨化转变，涂层的硬度减小。
关键词：含氢DLC涂层；退火处理；微观组织；力学性能；LAMMPS模拟中图分类号：TB332 文献标志码：A 文章编号：1001-3660(2024)05-0174-10DOI：10.16490/ki.issn.1001-3660.2024.05.018Effect of High-temperature on Microstructure and MechanicalProperties of Hydrogen-containing DLC CoatingJIA Weifei1, LIANG Canmian2, HU Feng1,2*(1. Collaborative Innovation Center for Advanced Steels, Wuhan University of Science and Technology, Wuhan 430081,China; 2. Guangdong Xinglian Precision Machinery Co., Ltd., Guangdong Foshan 528251, China)ABSTRACT: The thermal stability of hydrogen-containing DLC coating is poor, and the work aims to explore the microstructure changes of hydrogen-containing DLC coating at high temperature and their impact on mechanical properties. The收稿日期：2023-01-09；修订日期：2023-05-18Received：2023-01-09；Revised：2023-05-18基金项目：中国博士后科学基金（2021M700875）Fund：China Postdoctoral Science Foundation (2021M700875)引文格式：贾伟飞, 梁灿棉, 胡锋. 高温对含氢DLC涂层的微观结构及力学性能的影响[J]. 表面技术, 2024, 53(5): 174-183.JIA Weifei, LIANG Canmian, HU Feng. Effect of High-temperature on Microstructure and Mechanical Properties of Hydrogen-containing DLC Coating[J]. Surface Technology, 2024, 53(5): 174-183.*通信作者（Corresponding author）第53卷第5期贾伟飞，等：高温对含氢DLC涂层的微观结构及力学性能的影响·175·hydrogen-containing DLC composite coating with Si as the transitional layer was deposited on the surface of S136 stainless steel by plasma enhanced chemical vapor deposition (PECVD). The microstructure of DLC coating was investigated by optical/scanning electron microscopy, Raman spectroscopy, XPS (X-ray photoelectron spectroscopy) and three-dimensional profiler, the mechanical properties of DLC coating were studied by scratch, reciprocating friction wear and nano-indentation experiment, and the nano-indentation experiment behavior of DLC coating was simulated by LAMMPS to analyze the microstructure characteristics in annealing. The coating was subject to annealing conditions of 400 ℃for 2 hours and 600 ℃for 2 hours. Under the former condition, Raman spectroscopy showed an increase in the intensity ratio of the I D/I G peaks from0.7 to 1.5, indicating graphitization transition, accompanied by a decrease in baseline slope and H element segregation. XPSanalysis revealed an increase in sp2 hybridization and oxygen content in the coating under this condition, as well as an increase in surface roughness. At 600 ℃, severe oxidation of the DLC coating was observed. Under that condition, the matrix stainless steel was also oxidized. Molecular dynamics simulations using LAMMPS suggested a decrease in molecular bond length at 400 ℃high temperature. The three-dimensional profile test showed that the roughness under the unannealed condition was mainly from the large particles produced during deposition. At 400 for 2℃h, the coating had the minimum surface roughness. At this time, some large particles in the coating structure fell off, and the coating was basically completely damaged at 600 for℃ 2 h. The roughness was mainly from the original stainless steel roughness. The scratch test showed that under the condition of 400 for℃2 h, due to the release of the internal stress of the coating and the tighter bonding of the transition layer, the coating had the bestbonding effect with the substrate and was the least likely to fall off. The statistical results of LAMMPS simulation showed that the chemical bonds of the original DLC model tended to become shorter after annealing at high temperature. Relative to the unannealed DLC coating, the mechanical properties of DLC coating were best under 400 for℃ 2 h. Under this condition, the precipitation of mixed H elements in the coating led to the transformation of the original C—H sp3 structure, which occupied a large space to the smaller C—C sp3 and C—C sp2 structure, releasing internal stress in the coating, while ensuring the strength.The nano-indentation experiments showed that the elastic recovery and hardness of the coating were the highest at 400 for℃ 2 h, compared with that at other annealing temperature. The structure of the DLC coating containing hydrogen changed due to the precipitation of H element at 400 ℃. On the one hand, the coating structure changed from sp3 to sp2 due to high temperature, and on the other hand, the precipitation of H element changed the original C—H sp3 to C—C sp3, reducing the internal stress of the coating and improving the mechanical properties. The coating is basically damaged at 600 for 2 h, but the substrate still℃retains part of the coating. This is because the transition layer Si reacts with the coating to improve the heat resistance of the remaining coating. Molecular dynamics simulations using LAMMPS showed that the coating undergoes a graphitization transition at high temperature, leading to a reduction in its hardness.KEY WORDS: hydrogen-containing DLC coating; annealing treatment; microstructure; mechanical properties; LAMMPS simulationDLC（Diamond-Like Carbon，类金刚石碳，简称DLC）涂层材料具有超高硬度、低摩擦因数、优良化学稳定性等特点，广泛应用于机械、电子、生物医学等领域[1-3]。
EN1998--层合板喷覆成形
Keywords
carbon steel, hot corrosion, Si-base coating, thermal spray
1. Introduction
High-temperature alloys must have good mechanical properties and corrosion resistance and be relatively easy to manufacture. However, it is not likely for a single alloy to have all these properties. Most high temperature alloys are iron-, nickel-, or cobalt-base because these elements have high melting points and are easy to manufacture without problems. Unfortunately, their oxides are not protective enough in the combustion environment of a fossil-fuel power plant at temperatures above 550 °C. Nevertheless, addition of other elements to establish more protective oxides such as Cr2O3, Al2O3, or SiO2 has improved their corrosion resistance. These oxides offer protection due to their low growth rate and the effective barrier they provide against ionic migration (Ref 1-3). The threshold amount required in the alloy for the establishment of a continuous protective oxide layer depends on the alloying elements. Chromium affects the mechanical properties of the alloys the least, but a higher threshold value is required to allow a passive behavior against oxidation (16 to 20%). For aluminum additions, a threshold value of 15% is required (Ref 1, 2), whereas for silicon additions to steel the threshold value is the lowest, 5% (Ref 2, 4, 5). Although the addition of aluminum or silicon gives alloys the best oxidation and corrosion resistance because they form protective oxides with low growth rate, their incorporation can affect the mechanical properties of the alloy. It has been observed that a third element, normally chromium, which forms
高温高压简写英文
高温高压简写英文High Temperature High Pressure (HTHP) abbreviated English refers to a specific set of terminology used in the field of materials science and engineering related to extreme temperature and pressure conditions. HTHP conditions are often encountered in industrial applications such as high-temperature andhigh-pressure processing, materials synthesis, and testing.In order to facilitate communication and understanding among professionals in the field, a standardized system of abbreviations has been developed. These abbreviations are commonly used in research papers, technical reports, and international conferences to describe experimental setups, material properties, and testing procedures under HTHP conditions. This document aims to outline some of the most frequently used HTHP abbreviations and their corresponding meanings.1. P-T: Pressure-TemperaturePT refers to the simultaneous measurement of pressure and temperature. This abbreviation is often used to describe experimental conditions, such as PT phase diagram, which shows the relationship between different phases of a material as a function of pressure and temperature.2. HIP: Hot Isostatic PressingHIP is a process used to densify, consolidate, or sinter materials by applying simultaneous hightemperature and high pressure. This technique is commonly used in powder metallurgy, ceramics, and composite material processing to improve material properties such as density, porosity, and mechanical strength.3. HPHT: High Pressure High TemperatureHPHT refers to the conditions of both high pressure and high temperature. This abbreviation is often used to describe material synthesis or testing under extreme conditions. For example, HPHT diamond synthesis refers to the artificial production of diamonds using high pressure and high temperature.4. HPCS: High-Pressure Carbonaceous Sedimentary RocksHPCS refers to a type of rock formation composed of carbon-rich materials that have undergone high-pressure metamorphism. These rocks are often associated with deep subduction zones and are of great interest to geologists studying the Earth's dynamics.5. DAC: Diamond Anvil CellA DAC is a high-pressure cell often used in experiments to generate extreme pressures. It consists of two opposing diamonds that exert pressure on a sample placed between them. The DAC allows for measurements of material properties under high-pressure conditions.6. TGA: Thermogravimetric AnalysisTGA is an analytical technique used to study the thermal stability and decomposition behavior of materials. It involves continuously monitoring the sample's weight as it is heated or cooled. TGA is particularly usefulfor characterizing the decomposition or phase transitions of materials at elevated temperatures and pressures.7. DSC: Differential Scanning CalorimetryDSC is a technique used to measure the heat flow associated with a sample's phase transitions or chemical reactions. It provides valuable information about the thermal behavior of materials under HTHP conditions.8. RTILs: Room-Temperature Ionic LiquidsRTILs are a class of molten salts or liquid materials that remain in the liquid state at or near room temperature. These unique liquids possess excellent thermal stability and chemical resistance, making them ideal for various high-temperature and high-pressure applications.9. HTHP Synthesis: High-Temperature High-Pressure SynthesisHTHP synthesis refers to the production or creation of materials under extreme temperature and pressure conditions. It is often used to modify material properties, induce desired phase transitions, or synthesize new compounds with unique properties that are not achievable under normal conditions.10. HTHP Testing: High-Temperature High-Pressure TestingHTHP testing refers to the evaluation of material properties or behavior under extreme temperature and pressure conditions. This testing is crucial for understanding the response of materials in high-pressure environments, such as in oil and gas exploration or deep-sea exploration.In conclusion, HTHP abbreviated English provides a standardized system for communicating and understanding research related to extreme temperature and pressure conditions. The abbreviations discussed in this document are commonly used in scientific literature and discussions. Familiarity with these terms is essential for researchers and professionals working in the field of HTHP materials science and engineering.。
金属材料相关英语词汇（3）
金属材料相关英语词汇(3)弹簧用碳钢片carbonsteel strip for spring use冷轧状态 cold rolled strip回火状态 annealed strip淬火及回火状态hardened & tempered strip/ precision – quenched steel strip 贝氏体钢片 bainite steel strip弹簧用碳钢片材之边缘处理 edge finished淬火剂quenching media碳钢回火 tempering回火有低温回火及高温回火low & high temperature tempering高温回火high temperature tempering退火 annealing完全退火 full annealing扩散退火 diffusion annealing低温退火 low temperature annealing中途退火 process annealing球化退火 spheroidizing annealing光辉退火 bright annealing淬火 quenching时间淬火 time quenching奥氏铁孻回火 austempering马氏铁体淬火 marquenching高碳钢片用途 end usage of high carbon steel strip冷轧高碳钢–日本工业标准cold-rolled (special steel) carbon steel strip to jis g3311电镀金属钢片 plate metal strip简介 general电镀金属捆片的优点advantage of using plate metal strip金属捆片电镀层plated layer of plated metal strip镀镍 nickel plated镀铬 chrome plated镀黄铜 brass plated基层金属 base metal of plated metal strip低碳钢或铁基层金属iron & low carbon as base metal不锈钢基层金属 stainless steel as base metal铜基层金属copper as base metal黄铜基层金属brass as base metal轴承合金 bearing alloy简介general轴承合金–日工标准 jis h 5401bearing alloy to jis h 5401锡基、铅基及锌基轴承合金比较表comparison of tin base, lead base and zinc base alloy for bearingpurpose易溶合金 fusible alloy焊接合金 soldering and brazing alloy软焊 soldering alloy软焊合金–日本标准 jis h 4341soldering alloy to jis h 4341硬焊 brazing alloy其它焊接材料请参阅日工标准目录other soldering material细线材、枝材、棒材chapter five wire, rod & bar线材/枝材材质分类及制成品classification and end products of wire/rod铁线(低碳钢线)日工标准 jis g 3532low carbon steel wires ( iron wire ) to jis g 3532光线(低碳钢线)，火线(退火低碳钢线)，铅水线(镀锌低碳钢线)及制造钉用低碳钢线之代号、公差及备注ordinary low carbon steel wire, annealed low carbon steel wire,galvanized low carbon steel wire & low carbon steel wire for nailmanufacturing - classification, symbol of grade, tolerance andremarks.机械性能mechanical properites锌包层之重量，铜硫酸盐试验之酸洗次数及测试用卷筒直径weight of zinc-coating, number of dippings in cupric sulphate testand diameters of mandrel used for coiling test冷冲及冷锻用碳钢线枝carbon steel wire rods for cold heading & cold forging (to jis g3507)级别，代号及化学成份classification, symbol of grade and chemical composition直径公差，偏圆度及脱碳层的平均深度diameter tolerance, ovality and average decarburized layer depth冷拉钢枝材cold drawn carbon steel shafting bar枝材之美工标准，日工标准，用途及化学成份aisi, jis end usage and chemical composition of cold drawn carbonsteel shafting bar冷拉钢板重量表cold drawn steel bar weight table高碳钢线枝high carbon steel wire rod (to jis g3506)冷拉高碳钢线hard drawn high carbon steel wire(to jis g3521, iso-84580-1&2)化学成份分析表chemical analysis of wire rod线径、公差及机械性能(日本工业标准 g 3521)mechanical properties (jis g 3521)琴线(日本标准 g3522)piano wires ( to g3522)级别，代号，扭曲特性及可用之线材直径classes, symbols, twisting characteristic and applied wire diameters直径，公差及拉力强度diameter, tolerance and tensile strength裂纹之容许深度及脱碳层permissible depth of flaw and decarburized layer常用的弹簧不锈钢线-编号，特性，表面处理及化学成份stainlessspring wire – national standard number, charateristic, surface finish & chemical composition弹簧不锈钢线，线径及拉力列表stainless spring steel, wire diameter and tensile strength of springwire处理及表面状况finish & surface各种不锈钢线在不同处理拉力比较表tensile strength of various kinds of stainless steel wire under different finish圆径及偏圆度之公差tolerance of wire diameters & ovality铬镍不锈钢及抗热钢弹簧线材–美国材验学会 astm a313 – 1987chromium –nickel stainless and heat-resisting steel spring wire –astm a313 – 1987化学成份 chemical composition机械性能 mechanical properties305, 316, 321及347之拉力表tensile strength requirements for types 305, 316, 321 and 347 a1s1-302 贰级线材之拉力表tensile strength of a1s1-302 wire日本工业标准–不锈钢的化学成份(先数字后字母排列)jis –chemical composition of stainless steel (in order of number &alphabet)美国工业标准–不锈钢及防热钢材的化学成份(先数字后字母排列)aisi – chemical composition of stainless steel & heat-resistant steel(in order of number & alphabet)易车碳钢free cutting carbon steels (to jis g4804 )化学成份 chemical composition圆钢枝，方钢枝及六角钢枝之形状及尺寸之公差tolerance on shape and dimensions for round steel bar, square steelbar, hexagonal steel bar易车(快削)不锈钢 free cutting stainless steel易车(快削)不锈钢种类 type of steel易车(快削)不锈钢拉力表tensile strength of free cutting wires枝/棒无芯磨公差表(μ) (μ = 1/100 mm)rod/bar centreless grind tolerance易车不锈钢及易车钢之不同尺寸及硬度比较hardness of different types & size of free cutting steel扁线、半圆线及异形线flat wire, half round wire, shaped wire and precision shaped finewire加工方法manufacturing method应用材料material used特点characteristic用途end usages不锈钢扁线及半圆线常用材料commonly used materials for stainless flat wire & half round wire扁线公差flat wire tolerance方线公差square wire tolerance。
氧化锆干压成型预烧工艺流程
氧化锆干压成型预烧工艺流程Zirconia is a versatile material with excellent mechanical properties, high temperature resistance, and biocompatibility, making it widely used in various industries, such as aerospace, biomedical, and electronics. 氧化锆是一种具有优异机械性能、耐高温性能和生物相容性的多功能材料，被广泛应用于航空航天、生物医学和电子等各个行业。
Dry pressing is a common method for shaping zirconia into various components due to its cost-effectiveness and ability to produceparts with complex geometries. 干压成型是一种常见的氧化锆成型方法，因为它具有经济高效和能够生产具有复杂几何形状的零件的能力。
The pre-sintering process is essential in the production of zirconia components as it helps to remove organic binders and improve the strength of the green compact before the final sintering. 预烧工艺在氧化锆零件的生产中至关重要，因为它有助于去除有机粘结剂，并在最终烧结之前提高绿坯的强度。
During the pre-sintering process, the zirconia green compact undergoes a series of thermal treatments to remove the binders andimprove the density and strength of the material. 在预烧工艺过程中，氧化锆绿坯经历一系列热处理过程，以去除粘结剂并提高材料的密度和强度。
高温下钢材力学性能研究进展-建筑材料工程
结 构 工 程 师 Structural Engineers
Vol． 33 ，No． 1 Feb． 2017
高温下钢材力学性能研究进展
程园园 李春祥 曹黎媛
*
（ 上海大学土木工程系， 上海 200444 ）
摘
钢结构建筑发生火灾时， 钢材在高温条件下屈服强度、 弹性模量等材料特性出现退化， 导致钢 结构承载力降低。因此， 研究高温条件下钢材的材料特性具有重要意义 。 但目前国内外没有统一公式 要
［8 ］
分别为屈服点 f y 、 初始弹性模量 E0 、 比例极限 f p 、
·文献综述·
［8 ］
· 191·
结构工程师第 33 卷第 1 期
软化阶段的弹性模量 E t ， 各参数的计算公式参考 文献 。 第二种分段模型是直线和曲线结合的模型。 这类模型比较有代表性的是 EC3 规定的 模 型、
［10 ］ Poh 等［9］、 李毅等 提出的模型。 从对比结果可
Ｒesearch Progress on Mechanical Properties of Steel Material at High Temperature
CHENG Yuanyuan LI Chunxiang CAO Liyuan *
（ Department of Civil Engineering， Shanghai University，Shanghai 200444 ，China）
更加接近实际情况。
3
3． 1
屈服强度和弹性模量
屈服强度和弹性模量的定
Poh 模型能够准确地代表高温下钢材的 以看出， 应力应变关系， 并且通用性更强。李毅等人提出 的模型则更简便， 通过该模型， 只需常温下钢材的 屈服强度就可以求出某一温度下钢材的应力应 变关系整体曲线。 EC3 模型则更加实用， 它用七 个线性和抛物线方程表示出应力应变关系， 其中 包含强化部分， 其曲线模式参考文献 2． 2 连续光滑模型
Co基合金
HAYNES 25 (L605) TECHNICAL DATAType AnalysisDescriptionHaynes 25 is a cobalt-based alloy which combines good formability and excellent high-temperature properties. At 1800°F, Haynes 25 sheet has a 100 hour stress-rupture strength of 7000 psi. The alloy is resistant to oxidation and carburization to 1900°F.ApplicationsHaynes 25 has given good service in many jet engine parts. Some of these include turbine blades, combustion chambers, afterburner parts, and turbine rings. The alloy has also been used successfully in a variety of industrial furnace applications including furnace muffles and liners in critical spots in high temperature kilns.Corrosion ResistanceHaynes 25 (L-605) has displayed excellent resistance to the hot corrosive atmospheres encountered in certain jet engine operations. Resistance to oxidation is good for intermittent service up to 1600°F and continuous service up to 2000°F.Haynes 25 (L-605) is highly resistant to scaling and oxidation at elevated temperatures, with particularly good qualities under extreme oxidizing conditions.This material also possesses excellent resistance to chemical oxidizing agents, and extraordianry resistance to hydrochloric and nitric acids at certain concentrations and temperatures. Resistance to salt spray corrosion is very good.Heat TreatmentSolution Heat Treated for Best PropertiesFor optimum properties, most wrought products are shipped in the solution heat treated condition. This alloy is normally solution heat treated in the temperature range of 2150 to 2250°F, and then either rapid air-cooled or water-quenched. Sheet 0.025" thick or less is solution heat treated at 2150°F, rapid air cooled or water quenched.; over 0.026" and over, at 2200°F, rapid air cooled or water quenched; plate at 2200°F, water quenched; and bar at 2250°F, water quenched.Room and Elevated Temperature Properties Enhanced by Cold Work and AgingCold working and aging, when properly employed, improves both the room and elevated temperature tensile strength of Haynes 25 sheet. Moderate amounts of cold work will increase creep strength up to 1800°F and stress rupture strength at temperatures up to 1500°F. Aging produces no significant benefit. Strain aging, at 700 to 1100°F, however, improves creep and rupture strength below 1300°F.Physical Properties** ExtrapolatedDynamic Modulus of ElasticityMechanical Properties* Average properties ** Guaranteed minimum properties Typical Short-Time Tensile DataAverage Rupture DataWorkabilityMachinabilityHaynes 25 (L-605) is machinable using conventional techniques; however, cobalt grades of high-speed steel or carbide tools combined with rigid machine setups are recommended.Haynes 25 (L-605) is more difficult to machine than the austenitic stainless steels (i.e. Types 302, 304, 321, and 347 stainless). Generally, lower feeds, speeds and depths of cut are suggested. A very high work hardening rate, generation of heat during cutting and high shear strength complicate machining.WeldingHaynes 25 can be welded by shielded metal-arc, gas tungsten-arc (TIG) and gas metal-arc (MIG) methods. Submerged-arc welding is not recommended because this process is characterized by high heat-input to the base metal and slow cooling of the weld. These factors can lower weld ductility and promote cracking.CleaningThe joint surface and adjacent area should be thoroughly cleaned down to bright metal before welding. All grease, oil, crayon marks, and other foreign matter should be removed by scrubbing with trichlorethylene or some other suitable solvent. The surface should be wiped clean before welding.。