Research on the technology and properties for TIG welding of AZ31 magnesium alloys tube

Welds of AZ31 magnesium alloy was carried out using gas tungsten arc(GTA) welding.The microstructures of AZ31 magnesium alloy base metal,heat affected zone (HAZ) and weld metal were investigated by optical microscopy.The fusion line between weld metal and HAZ was distinct.The HAZ was overheated and the grain size was coarser.However,the grain size of weld,which was quenched like casting and fine equiaxed grains were formed,was smaller than that of base metal and HAZ.The discontinuous network phase, Mg17Al12 and Mg17 (AlZn)12 and divorced eutectic distributed around gain boundary in weld metal was detected.The hardness of weld metal was higher than HAZ,where was lower than base metal.