DP600/AZ31无匙孔搅拌摩擦点焊塑性金属流动特性及断裂行为研究

在最优焊接参数下，对1 mm DP600镀锌钢板和3 mm AZ31镁板进行无匙孔搅拌摩擦点焊试验，焊后对接头分别进行横切、纵切及层切，采用扫描电镜（SEM）分析焊接接头显微组织和断口形貌.结果表明，镁钢间的混合主要发生在搅拌针作用区域，形成“机械互锁”的组织形貌，有利于增加两种材料的有效接触，形成复相强化；轴肩作用区镁钢间搅拌不明显，界面较平滑，镁钢界面形成了金属化合物以及氧化镁，降低了接头的塑性和韧性.对DP600/AZ31无匙孔搅拌摩擦点焊焊接接头进行拉伸试验，发现焊接接头从搭接界面上断裂，断口呈“脉状花样”，为延性断裂.

Plastic metal flow characteristic and fracture behaviors of DP600/AZ31 with non-keyhole friction stir spot welding

With the optimum welding parameters, 1mm DP600 galvanized steel plateand 3mm AZ31 magnesium plate were welded by non-keyhole friction stir spot welding and transverse, longitudinal and level cutting sample were prepared, respectively, then microstructure and fracture morphology of joint were analyzed with SEM. The results show that magnesium and steel are mixed mainly in the pin stirring zone, and the "mechanical interlock" microstructure forms to increase the effective contact of the two materials to form composite enhancement.The interface of magnesium and steel at shoulder active region is smooth. In shoulder active region, intermetallic compounds and oxide form, which reduces the ductility and toughness of joint? Tensile tests of joint show the joints break away from the lap interface and fracture is ductile fracture with "vein pattern".