Study On Process And Properties Of ZL114A Cast Aluminum Alloy MIG Welding

ZL114A alloy is widely used in the aerospace, transportation and machine manufacturing fields, which is a kind of high strength and toughness cast aluminum alloy. But in the process of casting, ZL114 A will appear some defects inevitably. In order to raise the yield, the repair welding technology need to performed. The welding properties of ZL114 A aluminum alloy are investigated to explore reasonable welding technology, which is appropriate for ZL114 A alloy. ZL114 A aluminum alloy sheets are welded by MIG through changing weld rods, weld parameters and welding heat input. The contents includes: Droplet transfer behavior, the forming characteristics and defects of ZL114 A aluminum alloy welded joints; Optimize welding process and analysis microstructure and mechanical properties of ZL114 A alloy welded joints; The influence of welding parameters on joints microstructure and mechanical properties are discussed.According to different welding rods, post weld heat treatments are set to improve microstructure and mechanical properties of ZL114 A alloy welded joints.Evaluations are taken on the forming characteristics and defects. It shows that, welding current, arc voltage, welding speed and the flowing speed of shielding gas all have a very important influence on the welding process, and using suitable MIG welding technology can guarantee the ZL114 A cast alloy sheets’ connection without obvious defects.Respectively analysis of microstructure and mechanical properties are taken on two states of ZL114 A alloy welding joints. The size of crystalline grain of casting sheet is small due to rapid cooling rate, while base metal has coarse cast structure and more defects, so tensile fracture located in the base metal. The heat affected zone of cast-aging sheet joints including Laser-quenched Zone and Softening Zone, and the Softening Zone exhibits a trough in the hardness trace.Three welding rods are chosen for this experiment. Al-Si joint is filled with dendritegrains and more defects, while Al-Mg joint is filled with equiaxed grains and having no defects. So the mechanical property of Al-Mg joint is best. The grain size of pure aluminum welding joint is large, and grain boundary is not obvious, mechanical properties similar to pure aluminum.After the post weld heat treatment, the mechanical property of Al-Si joint improved obviously, tensile strengths achieved to 93%of base metal. Al-Si joint have no desirable post weld heat treatment, so mechanical property fail to improve.