2011-Al铝合金摩擦

2011-Al铝合金摩擦
2011-Al铝合金摩擦

Materials Science and Engineering B 168 (2010) 176–181

Contents lists available at ScienceDirect

Materials Science and Engineering

B

j 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 e

b

Friction and wear behavior of surface nanocrystallized aluminium alloy under dry sliding condition

N.Arun Prakash a ,R.Gnanamoorthy b ,?,M.Kamaraj c

a

Department of Mechanical Engineering,Indian Institute of Technology Madras,Chennai 600036,India

b

Indian Institute of Information Technology,Design and Manufacturing (IIITD&M)Kancheepuram,Chennai 600036,India c

Department of Metallurgical and Materials Engineering,Indian Institute of Technology Madras,Chennai 600036,India

a r t i c l e i n f o Article history:

Received 31July 2009

Received in revised form 31October 2009Accepted 4November 2009Keywords:

Controlled ball impact peening Surface nanocrystallization Aluminium alloy Friction Wear

a b s t r a c t

One way of improving the surface properties of engineering material is by reducing the grain size at the surface.Controlled ball impact process is developed for producing surface nanocrystallization and improves the surface mechanical properties by inducing compressive residual stress on the metallic materials.Improvement in the surface mechanical properties will affect the tribological properties.This paper reports the in?uence of the surface nanocrystallization on the tribological properties of aluminium alloy.Tribological properties were evaluated under dry sliding conditions using a reciprocating wear test facility.The friction coef?cient of the treated surface is lower than that of the untreated samples and treatment improves the wear resistance of aluminium alloys.The improvement in the friction and wear properties is due to enhancement of surface strength,due to grain re?nement and induction of compressive residual stress.The worn surfaces observed using scanning electron microscope reveal the dominant adhesive nature of wear and mild abrasive wear.

? 2009 Elsevier B.V. All rights reserved.

1.Introduction

In aerospace and automobile industry,many components experience wear and cyclic loading in service.Efforts are being continuously made to improve the hardness,strength and tri-bological properties of structural materials without changing the surface chemistry.One of the ways to improve surface properties of the metallic material is by producing a nanocrystalline sur-face layer with the introduction of compressive residual stress.Grain re?nement by severe plastic deformation at and near surface of the metallic materials is an economical method for produc-ing ?ne grained structure by deforming the material at very high plastic strain rates.Nanocrystalline materials are characterized by nanometer sized grains with a large number of grain boundaries [1].Grain re?nement and improvement in wear resistances,strength and hardness of the nanocrystalline materials gains its importance compared to the coarse grained materials [2].

Several surface deformation processes like ball milling,ultra-sonic shot peening,sandblast-annealing,high energy shot peening,surface nanocrystallization and hardening (SNH),equal channel angular extrusion,surface mechanical attrition technique (SMAT),supersonic ?ne particle bombardment (SFPB)and severe plastic

?Corresponding author.

E-mail address:gmoorthy@iitm.ac.in (R.Gnanamoorthy).

torsion straining are used to produce nanocrystalline surface lay-ers on metallic materials.To create a nanocrystalline structure on the surface layer of metallic materials,Controlled ball impact (CBI)peening process was developed.Nanocrystalline surface layer was produced on the surface of AISI 304stainless steel by controlled ball impact process [3].

A few research works has been published on the tribo-characteristics of nanocrystalline surfaces [4–8].The friction and wear resistance of nanocrystalline surface layer of low carbon steel and pure copper produced by surface mechanical attrition technique process shows a decrease in friction coef?cient and improved wear resistance [4,5].The nanocrystalline surface layer of 304stainless steel produced by sand blasting and annealing resulted in enhanced corrosion and wear resistance compared to conventional coarse grain structure [6].The friction and wear resistance of a nanocrystalline surface layer on quenched and tempered chrome–silicon alloy steel fabricated by supersonic ?ne particle bombardment sample are enhanced [7].Nanocrystalline aluminium alloys exhibit better wear resistance compared to coarse grain conventional alloys [8].

The objective of this paper is to investigate the effects of grain re?nement on the friction and wear properties on aluminium alloy using controlled ball impact peening.Tribological properties of nanocrystalline layer are studied in comparison with the untreated sample and reasons responsible for the enhancement in friction and wear properties of the treated surface are discussed.

0921-5107/$–see front matter ? 2009 Elsevier B.V. All rights reserved.doi:10.1016/j.mseb.2009.11.011

N.A.Prakash et al./Materials Science and Engineering B168 (2010) 176–181177

2.Controlled ball impact process

Controlled ball impact peening was carried out at a strain rate of 2320/s and the samples were precisely moved using programmable logic controlled linear actuator.High carbon high chromium hard-ened steel ball of2mm diameter is used for the treatment and it acquires the kinetic energy from the drive source.The guided high velocity ball impacts on the sample to be treated.Localized plastic deformation is developed on the sample by the ball impact.When the ball hits the target,the elastic/elasto-plastic deformation occurs in the contact zone.When the mean contact pressure developed due to ball impact reaches about1.07times the yield strength of target material,the material deforms plastically.The ball impact velocity is maintained constant at0.85m/s[3].Tests were carried out by varying the specimen traveling velocity which in?uences the peening pattern.After each pass in x-direction,the sample is moved in y-direction by1step(0.0254mm).Different sample traveling velocities(0.76,1.02,and1.27mm/s)are employed.The samples were treated for an approximate surface area of15mm×10mm.

3.Test materials and experimental details

Aluminium alloy,AA6063-T6,samples of dimension 25mm×10mm(surface area)were prepared for the treatment. Before subjecting to controlled ball impact peening treatment,all specimens were polished using different grades of silicon carbide abrasive paper up to a grit size of#1200and then polished using?ne particles of alumina powder.A surface roughness of 0.1±0.02?m(R a)was maintained in the samples prior to the ball impact treatment.The friction and wear tests were performed in the as-peened samples.

The indentation hardness and residual stress of the nanocrys-talline surface were evaluated using a dynamic ultra micro-hardness tester using Berkovich indenter.The grain size of the treated surface is quanti?ed using X-ray diffraction analysis and transmission electron microscope(TEM).Surface roughness of the treated and untreated samples was measured using a pro?lometer with a cut off length of0.25mm and traverse length of1.25mm.

Unlubricated friction and wear tests were performed in ambi-ent laboratory atmosphere using a reciprocating sliding wear test facility.The coef?cient of friction and wear rate of aluminium alloy6063-T6was studied by sliding against a high carbon high chromium steel ball of10mm diameter.The hardness of the hard-ened steel ball is60±2HRC.Sliding wear tests were performed on both untreated and as-treated samples for applied normal loads, 5and30N at a constant stroke length of5mm.All tests were performed for a sliding velocity of9.26×10?3m/s up to a sliding distance of150m.A precision load cell was used to measure the fric-tion force continuously and stored using a personal computer based data acquisition system.To calculate the weight loss and the corre-sponding wear rate,weight of the specimen was measured before and after the test using a precision electronic balance of0.01mg accuracy.The friction coef?cient and wear rate reported are the average values of three replicate test data for each test condition. The worn surface morphologies were investigated using scanning electron microscopy.Energy dispersive spectroscopy(EDS)was used to analyze the composition of various particles present on the worn surface and wear debris.

4.Results and discussion

4.1.Material characterization

Hardness and residual stress of the treated samples are determined from the load–depth curves obtained from microin-dentation experiments[9,10].Controlled ball impact peening resulted in signi?cant surface hardening and intensive peening at low sample traveling velocity resulted in high hardness.The indentation hardness of the top nanocrystalline surface layer is about1.2GPa and about twice of the matrix for sample treated at0.76mm/s and decreases gradually along the depth(0.58GPa in the matrix).The indentation hardness of the untreated sam-ple is585±10N/mm2.Hardness measurement conducted on the treated samples through the metallographically prepared cross-sectioned specimen revealed the depth of the hardened layer is about~300?m depending upon the sample traveling velocity[11]. Similar to other surface deformation process the magnitude of hardness produced by controlled ball impact process is high at the surface and decrease with increased distance from the treated surface[12,13].The enhancement in the surface hardness of the treated sample is mainly attributed to the generation of high den-sity dislocation with increased number of grain boundaries forming small grains,which restricts the dislocation motion rendering the material harder and stronger.

The reported values of residual stress are the average of?ve indentation test data.High load is required by the indenter to pen-etrate the treated surface at the same indentation depth compared to unpeened sample indicating compressive residual stresses are induced by the treatment.It is observed that the specimen peened at a sample traveling velocity of0.76mm/s showed higher com-pressive residual stress,165MPa on the treated surface compared to other peening conditions due to higher depth of hardened layer and severe plastic deformation[11].The magnitude of the com-pressive residual stress decreased with increasing distance from the surface.The uniform impact of the ball results in the forma-tion of uniform depth of compressive residual stress.The sample traveling velocity,duration of peening,coverage and number of overlapping impacts determined the depth of compressive residual stress produced.

The reported surface roughness values are the average val-ues of six measurements taken on each samples.The variation of centreline average surface roughness value(R a)measured on AA6063samples after the treatment are shown in Table1.There is a marginal increase in surface roughness in the treated samples depending upon the sample traveling velocity due to the occur-rence of severe plastic deformation at the impact zone.

The average grain size of the treated samples is estimated from the line broadening of X-ray diffraction peaks using Scherrer and Wilson method.The grain size,centreline average surface rough-ness(R a),indentation hardness,and compressive residual stress with different sample traveling velocities are shown in Table1.As the sample traveling velocity decreases,the grain size decreases with increase in the surface hardness and compressive residual stress.The samples peened at low sample traveling velocity experi-enced more number of impacts and resulted in enhanced hardness, compressive residual stress and grain re?nement.It is suggested that the strengthening of the treated samples is primarily due to the substantial grain re?nement.

Transmission electron micrographs illustrate the formation of equiaxed microstructure in the nanometer regime.The selected area electron diffraction pattern indicates these nanograins possess random crystallographic orientation.Transmission electron micro-scope dark?eld image and the corresponding selected area electron diffraction(SAED)pattern of the top surface layer of controlled ball impact treated sample with a sample traveling velocity,0.76mm/s are shown in Fig.1(a)and(b).The mean grain size of the nanocrys-talline surface layer is approximately8±2nm for the specimen peened at a sample traveling velocity,0.76mm/s.High strain and multi-directional loading imparted in the contact zone generates the localized multiple shear bands,deformation twins,high den-sity dislocation and dislocation pile-up which were responsible for

178

N.A.Prakash et al./Materials Science and Engineering B 168 (2010) 176–181

Table 1

Characteristics of the treated surfaces.Peening

condition Grain size (nm)Surface roughness,R a (?m)Indentation hardness (N/mm 2)Compressive residual stress (N/mm 2)Peened at 0.76mm/s 72±50.39

±0.021175±15165±6Peened at 1.02mm/s 96±80.44±0.021031±10126±4Peened at 1.27mm/s

128±10

0.52±0.03

976±10

105±4

Fig.1.TEM images of the treated specimen at a sample traveling velocity,0.76mm/s.(a)Dark ?eld images of the top surface layer and (b)selected area electron diffraction pattern.

Fig.2.Variation of coef?cient of friction for the unpeened and peened samples tested at a normal load,30N.

the nanostructured surface layer formation [11].Grain size quan-ti?ed from the X-ray diffraction pattern is shown in Table 1.X-ray diffraction analysis and TEM results clearly indicate the formation of ?ne grains in the treated samples.

4.2.Friction and wear behavior

Coef?cient of friction decreases during the initial state and then increases to attain a steady state of friction in all the samples investigated.The variation in friction coef?cient is the result of smoothening of asperities and entrapment of wear debris between the specimen and the counter part.Fig.2shows the variation of coef?cient of friction measured during the dry sliding tests con-ducted at an applied normal load of 30N of both as-annealed and as-treated samples.Fig.3(a)and (b)shows the initial and steady state coef?cient of friction plotted against the applied normal loads for different sample traveling velocity.The initial and steady state coef?cient of friction of the nanocrystalline surface is lower than the unpeened surface.The lower friction coef?cient of the surface nanocrystalline sample compared to the original sample might be

attributed to a decrease in the real area of contact due to increased surface hardness of the nanocrystalline layer and asperity penetra-tion [8,14].Coef?cient of friction decreases with decreasing grain size [15];similar phenomenon is observed in the controlled ball impact peened samples.Lower sample traveling velocity results in ?ne grain and smoother surface roughness [3].As the load is increased the steady state coef?cient of friction is drastically

Fig.3.(a)Initial coef?cient of friction plotted against applied load for different peening conditions.(b)Steady state coef?cient of friction plotted against applied load for different peening conditions.

N.A.Prakash et al./Materials Science and Engineering B 168 (2010) 176–181

179

Fig.4.Wear rate for samples tested at different applied loads and sample traveling velocity.

reduced.This phenomenon may be attributed to the friction cou-ples in contact during the sliding wear process.

As the sample traveling velocity increases,the surface rough-ness increases and compressive residual stress decreases thereby wear rate increases,since compressive residual stress dominate the process of wear [16].The wear rate is always lower for the treated samples compared to the untreated sample under the same test

condition indicating that surface nanocrystallization may effec-tively enhance the wear resistance of the material.Fig.4shows the wear rate for the sample treated with different sample traveling velocity.The decrease in wear rate and the improvement in wear resistance of the ball impact peened samples can be interpreted by Holms and Archards adhesive wear theory [17]as V =

PW H

(1)

which is applied to adhesive and abrasive wear,where V is the wear volume loss per unit sliding distance,W is the applied load,H is the hardness of the softer materials in the two members,P is the wear constant related to the wear mechanisms and the materi-als of the friction members.The wear loss obtained can be directly correlated to the hardness of the surface and wear resistance of the nanocrystalline surface layer,as hardness is enhanced due to the re?nement of the grain size [11].Presence of ?ne grain structure and compressive residual stress improves the surface strength of the material.High applied stresses due to the point contact may result in the crack initiation at the asperity contacts which propa-gates during successive sliding action.Presence of the compressive residual stress and high strength of ?ne grain material at the surface delays the crack initiation compared to the untreated sample.The crack tip blunting by the compressive residual stresses induced will also contribute to the reduction in the crack propagation velocity resulting in the reduced debris formation.The improvement in the wear resistance can be attributed to increase in the surface strength which is due to grain size re?ning and compressive residual stress

introduction.

Fig.5.Worn surface morphology of the unpeened and peened samples for a constant load of 30N.(a)Unpeened,Peened at sample traveling velocity,(b)1.02mm/s,and (c)1.27mm/s.Arrow indicates the direction of sliding.

180N.A.Prakash et al./Materials Science and Engineering B 168 (2010) 176–181

In addition,the increased hardness of the treated surface effec-tively prevents the penetration of particles to non-nanocrystallized zone during wear process and thereby decreases the wear rate.The materials peened at a low sample traveling velocity exhib-ited a good wear resistance due to the formation of the stronger ?ne grain hardened compressive stress induced layer compared to the other treatment conditions.Similar observation was reported in shot peened samples [18].The wear rate and wear depth of the treated samples are lower than that of the as-received samples indi-cating the load bearing ability of the treated samples are increased compared to unpeened samples.4.3.Wear morphology

The worn surfaces were observed using a scanning electron microscope to elucidate the predominant wear mechanisms.Fig.5shows the scanning electron microscope images of the worn sur-face of the treated and untreated sample for a load of 30N.At the initial stage more number of wear debris are generated which acts as a third body particle and accelerates the wear.The worn sur-face of the sample shows wear scars,craters and oxides.The wear

mechanism of the worn out samples is mainly adhesive and mild abrasive wear.Localized plastic deformation with severe adhesive wear was observed in the untreated samples.

To analyze the composition of various particles present in the wear track the EDAX analysis of the samples were performed.Fig.6shows the EDAX spectrum of the treated and untreated sample.Presence of oxygen in the wear track indicates the formation of oxide layer during the wear process and the wear associated with the breaking of oxide layer.The oxygen content in the untreated sample is high compared to treated sample.The untreated sample shows high plasticity and high rate of wear.Due to low surface hardness of the untreated sample,the continuous breaking of oxide layer occurs and hence wear rate increases.The presence of iron in the wear track indicates a material transfer has occurred between the specimen surface and counterpart.The presence of wear debris in the wear track reveals that wear particles get accumulated in the wear track itself during sliding.In case of the treated sample the higher hardness and low plasticity resists the removal of the material from the surface and oxygen level decrease as the breaking of the oxide layer decrease as compressive residual stress delay the wear

process.

Fig.6.EDAX spectrum of (a)unpeened and (b)peened at sample traveling velocity 1.27mm/s.

N.A.Prakash et al./Materials Science and Engineering B168 (2010) 176–181181

5.Conclusions

The tribo behavior of the nanocrystalline surfaces created by the controlled ball impact peening is investigated.Formation of?ne grain structure and presence of the compressive residual stress by the controlled ball impact process contribute to the improvement in the friction and wear characteristics of the aluminium alloys.The peening conditions in?uence the nature of surface layer formed (i.e.,the grain size,hardness,and compressive residual stress)and affect the tribological properties.The high strength surface layer delays the crack initiation and retards the crack propagation and contributes to the improvement of the wear resistance. References

[1]R.Bohn,T.Haubopld,R.Birringer,H.Gleiter,Scr.Metall.Mater.25(1991)

811–816.

[2]J.S.C.Tang,C.C.Koch,Scr.Metall.Mater.24(1990)1599.

[3]M.Kodeeswaran,R.Gnanamoorthy,Mater.Lett.62(2008)4516–4518.

[4]Z.B.Wang,N.R.Tao,S.Li,W.Wang,G.Liu,J.Lu,K.Lu,Mater.Sci.Eng.A352

(2003)144–149.

[5]Y.S.Zhang,Z.Han,K.Wang,K.Lu,Wear260(2006)942–948.

[6]X.S.Guan,Z.F.Dong,D.Y.Li,Nanotechnology16(2005)2963–2971.

[7]D.M.Ba,S.N.Ma,F.J.Meng,C.Q.Li,Surf.Coat.Technol.202(2007)254–260.

[8]M.Takagi,H.Ohta,T.Imura,Y.Kawamura,A.Inoue,Scr.Mater.44(2001)

2145–2148.

[9]W.C.Oliver,G.M.Pharr,J.Mater.Res.6(1992)1564.

[10]Q.Wang,K.Ozaki,H.Ishikawa,S.Nakano,H.Ogiso,Nucl.Instrum.Methods

Phys.Res.B242(2006)88–92.

[11]N.Arun Prakash,R.Gnanamoorthy,M.Kamaraj,Surface nanocrystallization of

316aluminium alloy by controlled ball impact technique(unpublihsed results).

[12]X.Wu,N.Tao,Y.Hong,B.Xu,J.Lu,K.Lu,Acta Mater.50(2002)2075–2084.

[13]G.Liu,S.C.Wang,X.F.Lou,J.Lu,K.Lu,Scr.Mater.44(2001)1791–1795.

[14]C.S.Montross,T.Wei,L.Ye,G.Clark,Y.W.Mai,Int.J.Fatigue24(2002)

1021–1036.

[15]R.Mishra,B.Basu,R.Balasubramaniam,Mater.Sci.Eng.A373(2004)370–373.

[16]U.Sánchez-Santana, C.Rubio-González,G.Gomez-Rosas,J.L.Oca?na, C.

Molpeceres,J.Porro,M.Morales,Wear260(2006)847–854.

[17]Wen Shizhu,Huang Ping,Tribology Principle,Tsinghua University Press,Bei-

jing,2003.

[18]S.Y.Ma,R.Chen,X.C.He,T.B.Li,X.Z.Hao,Acta Metall.Sin.41(2005)28–32.

几种铝合金焊接先进工艺

铝合金焊接的几种先进工艺:搅拌摩擦焊、激光焊、激光- 电弧复合焊、电子束焊。针对于焊接性不好和曾认为不可焊接的合金提出了有效的解决方法,几种工 艺均具有优越性,并可对厚板铝合金进行焊接。 关键词: 铝合金搅拌摩擦焊激光焊激光- 电弧复合焊电子束焊 1 铝合金焊接的特点 铝合金由于重量轻、比强度高、耐腐蚀性能好、无磁性、成形性好及低温性能好等特点而被广泛地应用于各种焊接结构产品中,采用铝合金代替钢板材料焊接,结构重量可减轻50 %以上。 铝合金焊接有几大难点: ①铝合金焊接接头软化严重,强度系数低,这也是阻碍铝合金应用的最大障碍; ②铝合金表面易产生难熔的氧化膜(Al2O3 其熔点为2060 ℃) ,这就需要采用 大功率密度的焊接工艺; ③铝合金焊接容易产生气孔; ④铝合金焊接易产生热裂纹; ⑤线膨胀系数大,易产生焊接变形; ⑥铝合金热导率大(约为钢的4 倍) ,相同焊接速度下,热输入要比焊接钢材大 2~4 倍。 因此,铝合金的焊接要求采用能量密度大、焊接热输入小、焊接速度高的高效 焊接方法。 2 铝合金的先进焊接工艺 针对铝合金焊接的难点,近些年来提出了几种新工艺,在交通、航天、航空等行业得到了一定应用,几种新工艺可以很好地解决铝合金焊接的难点,焊后接头性能良好,并可以对以前焊接性不好或不可焊的铝合金进行焊接。 2. 1 铝合金的搅拌摩擦焊接 搅拌摩擦焊FSW( Friction Stir Welding) 是由英国焊接研究所TWI ( The Welding Institute) 1991 年提出的新的固态塑性连接工艺[1~2 ] 。图1为搅拌 摩擦焊接示意图[3 ] 。其工作原理是用一种特殊形式的搅拌头插入工件待焊部位,通过搅拌头高速旋转与工件间的搅拌摩擦,摩擦产生热使该部位金属处于热塑性 状态,并在搅拌头的压力作用下从其前端向后部塑性流动,从而使焊件压焊在一起。图2 为搅拌摩擦焊接过程[4 ] 。由于搅拌摩擦焊过程中不存在金属的熔化,是一种固态连接过程,故焊接时不存在熔焊的各种缺陷,可以焊接用熔焊方法难以焊接的有色金属材料,如铝及高强铝合金、铜合金、钛合金以及异种材料、复合材料 焊接等。目前搅拌摩擦焊在铝合金的焊接方面研究应用较多。已经成功地进行了搅拌摩擦焊接的铝合金包括2000 系列(Al- Cu) 、5000 系列(Al - Mg) 、6000 系列(Al - Mg - Si) 、7000 系列(Al - Zn) 、8000 系列(Al - Li) 等。国外已经.进入工业化生产阶段,在挪威已经应用此技术焊接快艇上长为20 m 的结构件,美国洛克希德·马丁航空航天公司用该项技术焊接了铝合金储存液氧的低温容器火箭结 构件。 铝合金搅拌摩擦焊焊缝是经过塑性变形和动态再结晶而形成,焊缝区晶粒细化,无熔焊的树枝晶,组织细密,热影响区较熔化焊时窄,无合金元素烧损、裂纹和气孔等缺陷,综合性能良好。与传统熔焊方法相比,它无飞溅、烟尘,不需要添加焊丝和保护气体,接头性能良好。由于是固相焊接工艺,加热温度低,焊接热影响区显微组织变化小,如亚稳定相基本保持不变,这对于热处理强化铝合金及沉淀强化铝合金非常有利。焊后的残余应力和变形非常小,对于薄板铝合金焊后基本不变形。与

铝合金的搅拌摩擦焊

毕业设计说明书题目:铝合金的搅拌摩擦焊 姓名: 学号: 指导老师:

摘要 铝及铝合金是工业中应用最广泛的一类有色金属结构材料,铝合金具有良好的耐蚀性、较高的比强度和导热性以及在低温下能保持良好力学性能等特点,在航空航天、汽车、电工、化工、交通运输、国防等工业部门被广泛地应用。随着近年来科学技术以及工业经济的飞速发展,对铝合金焊接结构件的需求日益增多,使铝合金的焊接性研究也随之深入。铝合金的广泛应用促进了铝合金焊接技术的发展,同时焊接技术的发展又拓展了铝合金的应用领域,因此铝合金的焊接技术正成为研究的热点之一。 英国焊接研究所(The Welding Institute)发明的搅拌摩擦焊为轻金属材料的连接提供了新的方法和途径。自从搅拌摩擦焊摩擦焊发明以来搅拌摩擦焊技术得到广泛的关注和深入的研究。特别是针对铝合金材料,世界范围的研究机构学校以及大公司都对此进行了深入细致的研究和工程应用开发并且在诸多工业制领域得到了成功应用。 本文详细介绍了搅拌摩擦焊原理特点并且针对铝合金的搅拌摩擦焊特点性能以及工业应用作了详细的阐述同时对搅拌摩擦焊在中国市场的发展和应用作了简略介绍和预测。 关键词:铝及铝合金搅拌摩擦焊焊接方法焊接特点

Abstract Aluminum and aluminum alloy is a kind of nonferrous metal structure material widely used in industry, aluminum alloy has high corrosion resistance, good strength and thermal conductivity as well as in the low temperature can keep good mechanical properties and other characteristics, in the aerospace, automotive, electrical, chemical, transportation, national defense and other industrial sectors are widely used. In recent years with the rapid development of science and technology and industrial economy, structure of the growing demand for aluminum alloy welding, so the aluminum alloy welding research also further. Aluminum alloy is widely used to promote the development of welding technology of aluminum alloy, the welding technology development and expanding the application field of aluminum alloy, so the aluminum alloy welding technology is becoming one of the hot research topics. British Welding Research Institute (The Welding Institute) the invention of the friction stir welding for light metal materials is connected and provided a new approach to. Since the invention of the friction stir welding friction welding, friction stir widely attention and deeply research get welding technology. Especially for aluminum alloy material, worldwide research schools and large companies have conducted in-depth study and engineering application and has been successfully applied in many industrial fields. This paper introduces the principle and the characteristics of friction welding and stirring in aluminum alloy friction stir welding properties and industrial applications are described in detail the development and application of friction stir welding in the Chinese market are briefly introduced and predicted. Keywords: Aluminium and aluminium alloy Friction stir welding Welding process Welding characteristics

铝合金搅拌摩擦焊工艺分析研究

铝合金搅拌摩擦焊工艺研究 1. 本设计<课题)研究的目的和意义 1 搅拌摩擦焊在飞机制造中的优越性 搅拌摩擦焊技术从制造成本、重量和连接质量的角度考虑具有显著的优越性。例如,在飞机上的应用可以减少零件数量和库存,降低装配费用,减少设计成本,减少维修费用等。同时搅拌摩擦焊代替铆接可以降低接头重量。对于给定的应力水平而言,搅拌摩擦焊可以消除铆接和螺接的紧固孔引起的应力集中,提高飞机的疲劳性能和所必需的安全检验阈值以及时间间隔。消除板 - 板对接连接中的结合面,防止潮湿介质的入侵和腐蚀。消除不同材料紧固连接需要的紧固件和可能的电势腐蚀作用。免去密封介质和局部材料保护等。 1. 1 降低系统制造成本 搅拌摩擦焊技术为轻型铝合金结构的低成本、无紧固件的可靠连接提供了可能性,而且已经在航宇飞行器的制造过程中的成本控制上得到突破性进展。目前飞机制造中零部件的装配连接使用了大量的铆接和螺栓连接结构,如在空中客车A340飞机上使用了超过100万个铆钉。如果用搅拌摩擦焊接代替铆接,一方面搅拌摩擦焊具有比铆接更快的制造速度(因为搅拌摩擦焊准备简单,装配方便,操作程序少,焊接速度快>。另一方面搅拌摩擦焊不需要焊丝,不需要对接束缚条,不需要加强板,不需要粘接密封介质,没有紧固铆钉和高锁,在减少制造过程库存零部件的同时,大大减轻了飞机连接装配的重量。搅拌摩擦焊作为一种低成本的制造技术,用来代替气体保护熔化焊接( GMAW 和APPW> ,大幅度降低了系统费用。同时使单个燃料筒体的制造周期由原来的 23天,缩短为 6天。 1. 2 提高飞机制造效率 传统的飞机结构多为机械连接的装配方法,零件多,速度慢,制造步骤复杂,不容易实现生产装配自动化。但搅拌摩擦焊技术在飞机制造领域的应用,可使飞机高成本、大件加工、机械连接方式变为低成本、小件焊接、整体成型结构方式,有效提高了飞机制造装配的效率,缩短了飞机零、部件的制造装配周期。另外,搅拌摩擦焊技术对硬件要求较低,完全可以通过对传统机床设备的改造,或在现有机械设计和加工能力的基础上完成。而且焊接过程没有飞溅、电弧等强烈的电磁干扰,易于实现过程数字控制和生产自动化。目前国外公司已经在数控多坐标铣床和焊接机器人系统上应用搅拌摩擦焊技术,实现搅拌摩擦焊的变截面的空间曲线轨迹的焊接。波音公司已经成功地实现了复杂结构的飞机门的曲线搅拌摩擦焊焊接。另外在战斗机的裙翼上成功地实现了薄板 T 形接头的搅拌摩擦焊连接,并且进行了相关飞行测试。 1. 3 提供新的飞机结构设计可能性 搅拌摩擦焊不仅能在普通材料上得到优良的接头,而且在以前所谓的“难焊”和“不可焊接”铝合金材料上也能实现可靠连接,如可在1420、2195、2524、6013、6056、7075、Al MgSc等多种航宇合金材料上得到固相连接。同时,由于搅拌摩擦焊技术的特殊性,不同金属合金材料例如2524和7349,6065和1424,6061和2024等,也能得到可靠的焊接。对于从1 mm 到75 mm不同厚度的金属材料,基于搅拌摩擦焊不存在熔化过程,所以也能得到优良的固相连接。另外虽然原始材料的生产准备状态不同,但是搅拌摩擦焊可以实现板材件、挤压型材件以及预成型件的焊接。英国焊接研究所已经成功地把锻压板材件用搅拌摩擦焊的方法和铸态零件焊接在一起,同时得到非常优异的接头机械性能。搅拌摩擦焊技术为飞机结构设计中新材料、新结构的应用提供了更多的选择性和可能性。 2. 本设计<课题)国内外研究历史与现状 目前,该所主要是与航空、航天、船舶、高速列车及汽车等焊接设备制造厂和国际性的大

汽车用铝及铝合金搅拌摩擦焊技术条件

汽车用铝及铝合金搅拌摩擦焊技术条件 1 范围 本标准规定了汽车用铝及铝合金搅拌摩擦焊接的一般要求、焊前准备、焊接工艺、焊后检验和试验以及安全要求等。 本标准适用于汽车常用牌号和状态的铝及铝合金的搅拌摩擦焊接。其他系列铝合金搅拌摩擦焊接也可参照本标准。 2 规范性引用文件 下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件,仅所注日期的版本适用于本文件。凡是不注日期的引用文件,其最新版本(包括所有的修改单)适用于本文件。 GB/T 1173 铸造铝合金 GB/T 2651 焊接接头拉伸试验方法 GB/T 2653 焊接接头弯曲试验方法 GB/T 2654 焊接接头硬度试验方法 GB/T 3190 变形铝及铝合金化学成分 GB/T 3246.2 变形铝及铝合金制品组织检验方法第2部分:低倍组织检验方法 GB/T 3323 金属熔化焊焊接接头射线照相 GB/T 3375 焊接术语 GB/T 3880 一般工业用铝及铝合金板、带材 GB/T 6892 一般工业用铝及铝合金挤压型材 GB/T 11345 焊缝无损检测超声检测技术、检测等级和评定 GB/T 18851.1 无损检测渗透检测第1部分:总则 GB/T 27551 金属材料焊缝破坏性试验断裂试验3 术语和定义 GB/T 27552 金属材料焊缝破坏性试验焊接接头显微硬度试验 GB/T 32259 焊缝无损检测熔焊接头目视检测 GB/T 34630 搅拌摩擦焊铝及铝合金 3 术语和定义 GB/T 34630 搅拌摩擦焊铝及铝合金界定的术语和定义适用于本标准。 3.1 搅拌摩擦焊friction stir welding,FSW 利用高速旋转的搅拌头插入被焊材料后沿焊接方向运动,搅拌头与焊接材料产生摩擦热,使材料达到热塑性状态,实现工件间固相连接的焊接方法,见图1。

相关文档
最新文档