AZ71和AZ71E镁合金钨极氩弧焊焊缝微观组织对比研究

Comparison on Microstructure of TIG Weld Zone of AZ71 and AZ71E Alloy

采用TIG焊分别对AZ71和AZ71E镁合金薄板进行不填丝的焊接加工。焊后对其接头焊缝区组织进行对比观察发现:添加了富铈混合稀土的AZ71E镁合金焊缝区出现了胞状树枝晶,组织未得到细化。究其原因是由于稀土元素与Al结合生成新相Al11RE3,消耗了一部分Al量,从而减弱了Al对α-Mg晶粒的细化作用,导致晶粒粗化。

AZ71 and AZ71E alloy was welded without filler respectively by tungsten inert-gas（TIG）welding.After welding,the microstructure of weld zone was observed by optical microscope.It is found that the cellular dendritic grains appear in the weld zone of AZ71E,and with increasing the current,the grains cannot be refined.The cause is that RE element can not refine the grains,because RE and Al combine to form Al11RE3 and consume a little Al,which leads to the decrease of the grain refining effect,thus the grains become coarser.