基于网格重剖分的搅拌摩擦焊接数值模拟及搅拌头受力分析

采用自适应网格方法,建立搅拌摩擦焊接过程的完全热力耦合热刚粘塑性有限元模型,模拟搅拌摩擦焊接过程中工件的温度场、变形场和搅拌头的受力。计算结果表明,温度场关于搅拌头的分布为非对称,焊接在前行侧的有效应变高于其返回侧;沿焊缝区域的温度场、应变场分布是由工件的上表面至底面,呈自上而下的顺序递减。对搅拌头反力曲线的研究表明,在相同的转速下,焊接速度越快,其反力越大;在相同的焊接速度下,转速越大,其反力越小;搅拌头的受力峰值产生在预热阶段结束和搅拌头开始移动的时刻,在给定搅拌头倾角的情况下,搅拌头的最高温度产生在搅拌头的后侧。     

On the effect of tool offset in hybrid-FSW of copper-aluminium alloy

Tool offset is one the most significant parameters in joining of dissimilar materials by friction stir welding (FSW) process. An investigation is carried out on the effect of tool offset toward thermal history, material flow pattern, mechanical properties, welding force, and weld joint morphology. It was found that offsetting toward aluminum side along with a plasma-assisted heat source is an efficient approach to address one of the most important apprehensions in aluminum-copper solid-state welding process. The offset influences the amount of intermetallic at the joint interface and in-effect impacts on final strength and material flow behavior. The optimum and continuous layer of intermetallic produces the maximum weld joint strength. The specimen welded with optimum tool offset shows the highest strength using 55 A plasma current in hybrid friction stir welding process.     

6061铝合金无倾角搅拌摩擦焊工艺及性能

目的 为了适应空间曲面构件的搅拌摩擦焊,开展6061铝合金无倾角搅拌摩擦焊工艺及性能的研究。方法 采用无倾角搅拌摩擦焊用的搅拌头,对5 mm厚6061-T6铝合金板材进行试验,研究焊缝成形及接头力学性能,并分析接头组织特征。结果 零倾角搅拌摩擦焊接头从组织上可区分为5个不同区域：焊核区(WNZ)、热力影响区(TMAZ)、热影响区(HAZ)、轴肩影响区(SAZ)和母材(BM);随着搅拌头转速增加,焊缝宽度和焊核尺寸均先变大后变小;随焊接速度增加,焊缝宽度和焊核尺寸均逐渐变小;当焊接速度固定时,随搅拌头转速增加,接头拉伸强度先增加后减小;当搅拌头转速固定时,随焊接速度增加,接头拉伸强度逐渐增大。结论 采用无倾角搅拌摩擦焊接方法,能够实现对5 mm厚6061-T6铝合金板材的有效焊接。     

不锈钢外板对 2219 铝合金拼焊板胀形性能的影响

目的现有2219铝合金板材宽度不能满足大型复杂曲面件整体流体高压成形需要,仍需采用焊接方法制备成形坯料,焊缝的存在导致铝合金拼焊板整体性能不均匀,影响成形性能及壁厚分布。方法提出2219铝合金拼焊板的双层板流体高压成形方法,采用1.8 mm厚铝合金拼焊板作为内层板,1mm厚不锈钢板作为外层板,进行双层板胀形实验研究。对比分析了单层板与双层板条件下2219铝合金拼焊板的成形极限、应变及壁厚分布。结果外层板的存在能够使板材的极限成形高度和极限应变增加,同时使壁厚分布更加均匀。结论双层板之间存在界面摩擦,可以提高内层拼焊板的成形极限、改善壁厚分布。     

Effects of microstructural heterogeneity on very high cycle fatigue properties of 7050-T7451 aluminum alloy friction stir butt welds

In this study, the very high cycle fatigue (VHCF) properties of 7050-T7451 aluminum alloy and its friction stir welding (FSW) butt welds have been investigated. The results show that the failure of FSW joints still occurs at 7.0 × 10⁸ cycles. The fatigue properties of the FSW joints are superior to those of the base material, especially in the super long life regime. Most fatigue cracks initiate at the thermo-mechanically affected zone and heat affected zone on the advancing side of the FSW joints, and the susceptibility of these zones to fatigue is attributed to the metallurgical heterogeneity.     

Investigating the influence of tool shape during FSW of aluminum alloy via CFD analysis

This paper describes the application of the CFD code, Comsol Multiphysics, to modeling the 3-D metal flow in friction stir welding of AA 2024-T3 aluminum alloy in order to investigate the influence of tool shape over the metal flow. Heat transfer and non-Newtonian flow equations were solved simultaneously. The results from the benchmark experiments found in the literature were used for validation purposes. Scrolled shoulders and threaded pins were given as kinematic boundary conditions. This made the computational problem an easy one. A welding engineer can predict the metal flow around the tool with different scrolls and threads under any welding conditions without making expensive experiments. Investigation of the velocity field before actual welding can save a lot of engineering hours.     

船用5083铝合金厚板搅拌摩擦焊接工艺研究

研究了30 mm厚铝合金5083板材双面对接焊不同焊接速度和旋转速度的焊接参数组合对焊接接头成型质量及力学性能的影响,结果表明,当焊接参数处于旋转速度为400 r/min~600 r/min,焊接速度为80mm/min~120 mm/min的工艺参数窗口内时,可以获得焊缝成型质量与抗拉性能优异的焊缝。     

焊后时效处理对6082-T6铝合金搅拌摩擦焊接头的影响

对6082-T6铝合金搅拌摩擦焊接头进行自然时效和人工时效处理,通过透射电子显微镜、扫描电子显微镜、拉伸实验机和显微硬度计对组织演变和力学性能进行研究。结果表明:人工时效处理后显微硬度比焊态和自然时效高10~25HV,提高焊核区和热机影响区硬度效果明显好于自然时效。经过焊后自然时效、人工时效的焊接接头力学性能得到一定程度的提升,人工时效析出相比自然时效析出相抗拉强度提高12%,延伸率降低9%,人工时效提高拉伸强度效果更明显。人工时效处理后,焊核区组织发生显著变化,NZ主要为GP区,经过人工时效后NZ强化效应随团簇和GP区尺寸增大及数量增多而加强。HAZ主要为粗大的β′,经过人工时效后变化不大,硬度基本保持不变。通过对微观组织进行研究发现析出物的形状由界面能和应变能决定。     

镁合金搅拌摩擦焊接头晶粒取向和织构分析

利用背散射电子衍射分析技术(EBSD)和取像显微分析技术(OIM),通过定量测量变形镁合金AZ80A搅拌摩擦焊搭接接头的焊核区晶粒取向和织构,探讨了搅拌摩擦焊焊核区形成的微观过程.结果表明:AZ80A合金在搅拌摩擦焊过程中,存在塑性变形和动态再结晶两种微观过程,导致焊核区所形成的晶粒织构密度不强、取向呈多样化的趋势;晶粒为再结晶细晶粒;在焊核区,变形织构{1,-1,0,4}<1,0,-1,0>略偏离板法向20°,且随板厚方向向下越来越强,同时再结晶取向越来越多;焊核区晶粒继承了母材中的{1,-1,0,4}<1,0,-1,0>变形织构,在焊核区所发生的动态再结晶含有一定程度的原位再结晶.