Magnesium Alloy Welding Wires Prepared By Hot-Extruded And Welding Performance

The technology for preparation of AZ31,AZ91 magnesium alloys welding wire by hot extrusion process was studied. The AZ31,AZ91 magnesium alloys welding wires were successfully prepared after the confirmation of the technological parameters, such as: extrusion temperature, extrusion speed and extrusion force, etc. Microstructure and mechanical properties of magnesium alloys welding wire were also analyzed. The nice bonding of welding joint was obtained by using TIG with AZ31,AZ91 magnesium alloys filler wire under rational welding condition. AZ31 and AZ91 magnesium alloys welding wire withφ3mm andφ4mm can be prepared by hot-extrusion when extrusion temperature is 420℃, extrusion speed is 0.8m/min～1m/min and extrusion force is 9×10⁵N. The welding wires have smooth and bright surface and good performance. Scratched and rough surface appeared when the extrusion temperature is too low, while hot crack emerges when the extrusion temperature and extrusion force are too high.The microstructure of hot extruded AZ31,AZ91 magnesium alloys welding wire were refined. Grain size of AZ31 was 5μm¹5μm, grain size of AZ91 was 10μm～30μm. Compared with as-cast AZ31 alloy, the tensile strength of the wires increases about 25%, elongation doubles, the hardness of AZ31 promotes by 85%. and the hardness of AZ91 promoted about 26.8%.The grain size decreased and theβ-Mg₁₇Al₁₂ phase increased at the grain boundary in the weld joint when the AZ31 welding wire was used to weld AZ31 plates by TIG.. While AZ31 bases was welded with AZ91 welding wire, theβ-Mg₁₇Al₁₂ phases in the weld joint discontinuously surrounded the grain boundary and there are moreβ-Mg₁₇Al₁₂ phases in weld zone and heat affected zone than in the base.The higher welded joint strength was obtained when magnesium alloys welding wire wasused for AZ31 base welding. When using AZ31 magnesium alloys welding wire, the tensile strength of welded joint increased by 83%, and reached to 210MPa. When using AZ91 magnesium alloys welding wire, tensile strength of welded joint was 187MPa and increase by 74%. The elongation of AZ31 welded joint using AZ31 and AZ91 magnesium alloys welding wire were 2.5% and 2.1%, respectively. The hardness of welded joint using AZ91 magnesium alloys welding wire is higher than that of using AZ91. The hardness variation in weld joints with different weld filler is the same, that is hardness in weld zone was highest, and the hardness in the base was higher than that in the heat affected zone.