基于CEL方法的Al/Mg搅拌摩擦焊温度场及材料混合流动研究

Temperature Field and Material Mixing Flow in Friction Stir Welding of Dissimilar Al/Mg Alloys Based on CEL Approach

基于耦合欧拉-拉格朗日(coupled Eulerian-Lagrangion,CEL)方法建立AA5A06铝合金与AZ31B镁合金对接搅拌摩擦焊接(friction stir welding,FSW)的全热力耦合数值模型,并结合试验测试对Al/Mg异种金属FSW过程的温度场及材料混合流动特征进行研究。数值模拟所得特征点的温度循环曲线、焊缝表面形貌以及横截面上异种材料的混合分布状态均与试验结果吻合良好。在此基础上,采用质点追踪法对材料混合流动行为进行了深入分析。结果表明,高温区集中分布在轴肩下方区域,返回侧(镁侧)温度较低,温度梯度较大。焊缝区上表面材料熔合线偏向于前进侧(铝侧)。搅拌针附近材料流动剧烈,前进侧和返回侧的大部分材料都较均匀地沉积于搅拌针后方。前进侧与返回侧材料在水平和竖直方向上的交叉混合流动,促使最终形成了2种材料“咬合式”的结合界面特征。

A fully coupled thermo-mechanical numerical model is developed for the friction stir welding(FSW) of AA5A06 aluminum alloy and AZ31B magnesium alloy based on the coupled Eulerian-Lagrangian(CEL) method,and the temperature field and material mixing flow characteristics during FSW process are studied by numerical simulation and experimental tests.The temperature cycle curves,the weld surface morphology,and the mixed distribution of dissimilar materials on the cross section obtained by numerical simulation are in good agreement with the experimental results.On this basis,the particle tracking method is used to analyze the mixing flow behavior of dissimilar materials.The results show that the high temperature zone is located in the region below the tool shoulder,and the temperature in the retreating side(Mg side) is lower and its gradient is larger.The fusion line of dissimilar materials on the top surface is inclined to the advancing side(Al side).The materials near the pin flow significantly and most of the materials deposit evenly on the advancing and retreating sides behind the pin.The mixing flow of the materials on the advancing and retreating sides in the horizontal and vertical directions finally forms the zig-zag interface characteristics between the two kinds of materials.