AZ91B镁合金TIG焊接头组织与性能

Microstructure and Properties of TIG Welding Joint for AZ91B Mg Alloy

使用AZ61和AZ91焊丝TIG焊AZ91B镁合金均可获得组织致密、焊缝与母材结合良好的焊接接头。焊缝组织由分枝发达、呈雪化状的α枝晶以及晶间 (α +Mg17Al12 )低熔点共晶体组成 ;熔合区组织由细小的α Mg等轴晶和晶间共晶体组成 ;热影响区组织接近母材 ,由粗大的α Mg树枝晶和分布于其间的α +Mg17Al12 共晶体组成。由于焊接过程中镁的过热蒸发 ,导致焊缝相对含Al量升高 ,共晶体含量增多 ,从而使焊缝热裂纹倾向增大。使用ERAZ61焊接AZ91B合金更易获得抗热裂性能高、与母材成分和组织一致性好的接头 ;

Welding joint with sound microstructure and perfect bonding between the weld and AZ91B Mg base alloy can be obtained with AZ61 and AZ91 welding wire by TIG.The microstructure of the weld is composed of snowy α Mg dendrite with developed branches and interdendrite eutectic (α+Mg 17 Al 12 ) with low melting point.The microstructure of bonding zone consists of fine equaixed α Mg and interdendrite eutectic,while the microstructure of heat affected zone is very similar to those of base materials,consisting of coarse α Mg dendrites and interdendrite eutectic (α+Mg 17 Al 12 ).Due to the super heated vaporization of Mg atom during welding,the Al content and eutectic content in the weld increase,resulting in the increase of hot crack tendency in the weld.In the case of using ERAZ61 wire,the joint consistent with base materials in composition and microstructure exhibits high crack resistance,high tensile strength and elongation.Therefore,taking comprehensive consideration for welding technology and mechanical properties of the jiont,the ER AZ61 welding wire should be selected preferably.