Evolution of residual stress field in 6N01 aluminum alloy friction stir welding joint

Based on the characteristics of friction stir welding（ FSW） and Coulomb friction work theory,the residual stresses field of FSW joints of 6 N01 aluminum alloy（ T5）,which was used in high speed train,were calculated by using the ANSYS finite element software. During the FEM calculation,the dual heat source models namely the body heat source and surface heat source were used to explore the evolution law of the welding process to the residual stress field. The method of ultrasonic residual stress detecting was used to investigate the residual stresses field of the 6 N01 aluminum alloy FSW joints. The results show that the steady-state temperature of 6 N01 aluminum alloy during FSW is about 550 ℃,and the temperature mutates at the beginning and at end of welding. The longitudinal residual stress σ;is the main stress,which fluctuates in the range of-25 to 242 MPa. Moreover,the stress in the range of shaft shoulder is tensile stress that the maximum tensile stress is 242 MPa,and the stress in the outside of shaft shoulder is compressive stress that the maximum compressive stress is 25 MPa. The distribution of the tensile stress in the welding nugget zone（ WNZ） is obviously bimodal,and the residual stress on the advancing side is higher than that on the retreating side. With the increasing of the welding speed,the maximum temperature decreased and the maximum residual stress decreased when the pin-wheel speed kept constant. With the increasing of the pin-wheel speed,the maximum temperature of the joint increased and the maximum residual stress increased when the welding speed was constant. The experimental results were in good agreement with the finite element results.

Effect of Friction Coefficient on Deep Drawing of 6A16 Aluminum Alloy for Automobile Body

Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under friction coefficient ranging from 0 to 0.22.The lubricants selected for the tests were mechanical oil,butter and dry film lubricant,and the friction coefficient of these lubricants were 0.05,0.10 and 0.15,respectively.Microstructural evolution of 6 A16 aluminum alloy plate during drawing forming was investigated by OM,SEM and EBSD.The results showed that,with the increase of friction coefficient,the stress,strain and deformation degree in deformation zone increased,while the grain size in deformation zone decreased.Thus,the hardness of the cup-typed component increased with the increase of friction coefficient.Butter-lubricated cups had the highest tensile strength and yield strength after paint-bake cycle.The combination of simulation results and microstructure analysis of 6A16 aluminum alloy plate after drawing forming indicates that the appropriate lubricant is butter.

Dynamic experimental studies of a6n01s-t5 aluminum alloy material and structure for high-speed train

In this study, we focus on the dynamic failure property of A6N01S-T5 aluminum alloyusing for high-speed train. The method of SHBT+3D DIC was put forward to figure out the dynamic mechanical properties and dynamic failure strain of A6N01S-T5 aluminum alloy,and on the basis of this, Johnson-Cook model constitutive parameters and dynamic failure strain parameters were obtained through a series of static and dynamic tests.An important character of this methodwas that the sandwich structure from the true high-speed train was used in penetration test,followed by the numerical calculation of the same working condition using LS-DYNA.Then we compare the experimental results with simulation results mentioned above in terms of failure morphology in structure and the bullet speed throughout the entire process to verifythe accuracyof the parameter. The experimental results provide a data basis for the crash simulation model of high-speed trains,in turn to optimize the structural design and whole efficiency.

The influence of gradient mismatches on mechanical properties and microstructure of 2219-T6 aluminum alloy VP-TIG joints

In this paper,6 mm thick 2219-T6 aluminum alloy was joined by means of variable polarity tungsten-arc welding( VP-TIG) and the influence of gradient mismatches on VP-TIG joints is investigated. The average tensile strength of the joints reduces 32%,53% and 59%,when the mismatch of the joint was 0. 635 mm,1. 44 mm,1. 83 mm,respectively.Incomplete penetration,additional bending moment( Ma) and decrease of effective load region area are considered to explain this phenomenon. The fracture location of tensile specimens occurred at the weld zone( WZ) close to partial melt zone( PMZ),corresponding to a sharp decline of microhardness from PMZ to WZ. The original position of fracture is found at weld toe,where incomplete penetration forms due to the introduction of gradient mismatches.

Nickel-coated Steel Stud to Aluminum Alloy Joints Made by High Frequency Induction Brazing

Nickel-coated 45 steel studs and 6061 aluminum alloy with 4047 A1 alloy foil as filler metal were joined by using high frequency induction brazing. The microstrueture of Fe/A1 brazed joint was studied by means of optical microscopy （OM）, scanning electron microscope （SEM）, energy dispersive X-ray （EDX）, and X-ray diffraction （XRD）. Results showed that 45 steel stud and 6061 aluminum alloy could be successfully joined by high frequency induction brazing with proper processing parameters. The bonding strength of the joint was of the order of 88 MPa. Ni coating on steel stud successfully avoided the generation of Fe-AI intermetallic compound which is brittle by blocking the contact between A1 and Fe. Intermetallic compounds, i e, AI3Ni2, AlmNi0.9 and A10.3Fe3Si0.7 presented in AI side, FeNi and Fe-A1-Ni ternary eutectic structure were formed in Fe side. The micro-hardness in intermetallic compound layer was 313 HV. The joint was brittle fractured in the intermetallic compounds layer of A1 side, where plenty of A13Ni2 intermetallie compounds were distributed continuously.

Effects of nugget alloying on microstructures and properties of resistance spot welded joints of aluminum and steel

The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg2Si particles. The interface zone had a double-layer structure： Fe2Al5 layer at steel side and Fe4Al13 layer at Al nugget side. The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains. When alloy elements Cu, Zn, Ti and Ni were added, the tensile shear load of Al-steel joints reached 2 780 N, 2 910 N, 2 915 N and 2 929 N respectively, which increased by 24. 1%, 29.9%, 30. 1% and 30. 7% respectively compared with that （2 241 N） of joint without nugget alloying. Therefore, it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.

6×××系铝合金车体型材粗晶的研究进展

6×××系铝合金作为可热处理强化的中高强度铝合金,具有优良的可焊性和耐蚀性,在轨道交通领域已得到广泛应用。然而,粗晶环的存在严重影响了其作为结构材料的优良性能。介绍了铝型材粗晶产生原因,总结了减小轨道车体用6×××系铝合金型材的晶粒度和粗晶环厚度的措施,包括合金化学成分调整,均匀化退火、挤压工艺和热处理工艺的优化,模具结构调整等。

Effect of Conventional and Pulsed TIG Welding on Microstructural and Mechanical Characteristics of AA 6082-T6 Repair Welds

Repair welding of AA 6082-T6 joints was carried out using ER 4043 filler through the TIG welding process with or without pulsed current.Microstructure and mechanical characteristics of the joints before and after repairing were investigated by examining macrostructure,microstructure,and distributions of porosity in the weld metal(WM),and by hardness,tensile,and bending tests.We observed that the welding current,phase transformations in heat-affected zone(HAZ)and porosity introduced in the WM during welding influence on its mechanical properties in sequence.The experimental results showed that the bead width and penetration as well as size of pores in the joints were mainly influenced by the welding currents.The sound joints were obtained at a welding current of 140 A with or without pulsed current when welding speed and gas flow rate were set at 20 cm·min-1 and 15 L·min-1,respectively.Among them,the decrease in mechanical properties of repair weld(RW)was directly related to the phase transformations in the over-ageing zone due to the double welding thermal cycles and elevated distribution of porosity in the WM.In addition,it was observed that the comparatively smaller grain size and lower porosity in WM of the RW produced by pulsed TIG welding gave a positive effect on its mechanical properties.

6×××系铝合金微合金化的研究进展

6×××系(Al-Mg-Si)铝合金作为综合性能良好的中强铝合金,在航天工业和民用等领域具有广阔的应用前景,微合金化是提高铝合金性能的有效途径,也是研制新型铝合金的重要手段,是国内外铝合金研究的热点之一。综述了6×××系铝合金中元素Mg、Si、Cu、Mn、Sr、Zr、Sc等的作用,探讨了该系铝合金目前存在的问题和发展方向,指出了寻求廉价且有效的微合金化元素、进一步探明微合金化作用机理和复合微合金化是今后研究的主要方向。

6×××铝合金热处理工艺的研究概况

概述了6×××铝合金热处理工艺的国内外研究现状,分析了目前6×××铝合金热处理应用中存在的问题和研究工作中的不足,指出了未来研究和开发中需要解决的问题,并提出了具体的建议。

6×××系铝合金的晶间腐蚀评价方法研究

采用腐蚀深度法和质量损失法分别对6×××系铝合金的晶间腐蚀敏感性进行评价,并借助金相显微镜和扫描电镜对晶间腐蚀形貌和腐蚀产物进行观察和分析,从而选择适宜的晶间腐蚀评价方法。结果表明:6×××系铝合金具有一定的晶间腐蚀敏感性,其评价方法宜选择腐蚀深度法,腐蚀溶液为57gNaCl+10mLH_(2)O_(2)/1000m L H_(2)O,腐蚀温度为30℃,时间为24h。

2024铝合金与AZ91镁合金的C_(2)Cl_(6)除气研究

对比研究了C_(2)Cl_(6)对2024铝合金及AZ91镁合金的除气效果。结果表明,2024铝合金及AZ91镁合金的最高除气率可分别达44.8%及41.8%,此时熔体含氢量分别达到0.096 cm3/(100 g)和11.3 cm3/(100 g)。就添加量而言,AZ91镁合金比2024铝合金所需的C_(2)Cl_(6)添加量要大一些(前者为2%~3%,而后者约为1%)。C_(2)Cl_(6)对AZ91镁合金有明显的细化效果。并测试和分析了除气后合金的力学性能。除气后,铝合金和镁合金的力学性能均提高。

汽车用6×××系铝合金及其冲压成形性研究综述

铝合金具有比强度大、成形性好、导热性好、耐腐蚀及性价比高等优点,能够满足汽车轻量化的需求。对6×××系铝合金板材的研究现状作了综述,主要内容包括6×××系铝合金的合金元素、织构、力学性能和冲压成形性。6×××系铝合金板材与钢板相比,其成形性、刚度和抗凹陷性都较低,为使合金板材更好地满足汽车轻量化的需求,应综合考虑合金元素、织构、热处理状态和成形工艺等方面对成形性能的影响,优化合金板材的冲压成形性,研制出综合性能更优的车身板材,以提高汽车车身用铝量。

采用E2EM模型预测LaB_(6)相作为Al-Si-Cu-Mn耐热铝合金中初生富Mn相形核基底潜力及其细化效果

通过E2EM模型预测LaB_(6)相作为Al−Si−Cu−Mn耐热铝合金在凝固过程中出现的初生Al_(13)Mn_(4)Si_(8)相异质形核基底的潜力。LaB_(6)相和Al_(13)Mn_(4)Si_(8)相间共有5对位向关系满足E2EM模型的判定标准,其中一对晶面关系((110)LaB_(6)//(110)Al_(13)Mn_(4)Si_(8))被TEM观察证实。这表明LaB_(6)相可作为Al_(13)Mn_(4)Si_(8)相的有效异质形核基底。将1.0%(质量分数)的Al−2La−1B中间合金添加到Al−12Si−4Cu−2Mn合金中,并通过组织观察和力学性能测试来评价细化效果。实验结果表明,添加Al−2La−1B中间合金能显著细化初生Al_(13)Mn_(4)Si_(8)相,证实E2EM模型预测的结果。但初生Al_(13)Mn_(4)Si_(8)相的细化并没有提高合金的强度,这是由于铝基体与初生Al_(13)Mn_(4)Si_(8)相之间的弹性模量差大于Al_(15)Mn_(3)Si_(2)相。

6×××系变形铝合金的合金化原理和生产应用

较系统地叙述了6×××系变形铝合金的合金化原理,生产过程中材料成分、组织和性能之间的关系,主要元素Mg、Si及添加元素Cu、Mn、Cr的作用,杂质元素Fe的影响。介绍了有代表性的工业6×××铝合金的特点,以及生产、应用情况。

高强耐热6×××系铝合金的研究现状及其发展趋势

6×××系铝合金由于其密度低、易成形、耐蚀性好等优点,广泛应用于汽车及建筑领域。随着对6×××系铝合金使用要求的不断提高,人们对该系铝合金的强度及耐热性提出了更高的要求。介绍了微合金元素Mn、Cr、Fe、Zr、Sc等对6×××系铝合金组织及性能的影响,复合微合金化及Al_(3)(Sc,Zr)等复合粒子对提高6 xxx系铝合金力学性能的作用。综述了传统的轧制工艺及新型轧制变形工艺对6×××系铝合金组织及性能的影响,国内外对6×××系铝合金耐热性的研究现状,对6×××系铝合金的热处理强化手段进行概述,并对高强耐热6×××系铝合金的发展趋势进行展望。

6系铝合金的挤压粗晶环

为了了解铝合金挤压时的表面行为及粗晶环的来源和机制,进行了小规模的反挤压试验。为了知道工件条件和化学成分对其影响,对制件做了金相和定向条像显微照片观察,发现降低再结晶抑制元素(如Cr)含量,增大挤压比和挤压速度都会增大粗晶环的深度。基于挤压时显微组织的演变,提出了在制件外表生成粗晶环的机制。

两种不同Cu含量的6×××铝合金铸锭的均匀化工艺研究

通过扫描电镜(scanning electron microscopy)、差示扫描量热仪(differential scanning calorimetry)及热力学相图计算(calculation of phase diagram),研究了两种不同Cu含量的6×××铝合金铸锭的均匀化退火工艺。研究结果表明:对于低Cu含量的6×××铝合金(w(Cu)=0. 35%)在560℃保温10 h即可完全溶解Mg2Si相;提高Cu含量(w(Cu)=0. 9%),不仅低熔点结晶相种类增加、其体积分数增加,而且熔化温度降低,此时需采用双级均匀化退火制度535℃10 h+550℃20 h。

界面微结构对PA6/铝合金连接性能的影响

采用抛光或抛光-化学刻蚀对铝合金表面进行预处理,获得微纳米结构表面,再利用自制模具对铝合金与尼龙6(PA6)进行热压成型。用扫描电镜、激光共聚焦显微镜观察发现,硫酸刻蚀形成的微纳米结构表面有利于树脂在铝合金表面形成良好的机械互锁结构,实现PA6/铝合金优良的连接性能。力学性能测试显示,硫酸刻蚀后的PA6/铝合金连接试样拉伸剪切强度达到了19. 1 MPa,界面粘结性能最优,比抛光后的连接试样提高了870%,其失效模式由界面失效变为内聚失效。

6×××系铝合金薄板预时效工艺探索

通过分析国内外有关6×××系铝合金薄板预时效工艺优劣特点,制定了适合我公司的预时效工艺方案。实验结果表明:6×××系铝合金薄板在560℃、120s固溶淬火后进行短时预时效可以达到预期的性能,通过一定程度的提高预时效温度或延长保温时间,合金板材的烤漆硬化性能得到增强,但过高的预时效温度不利于板材的冲压性能,最佳预时效工艺为150℃/1min。