Microstructural evolution and mechanical properties of semisolid stir welded zinc AG40A die cast alloy

A high quality joint of zinc based pressure die cast alloys can be hardly achieved by conventional fusion welding. In this study, a novel technique to achieve the globular weld structure using stirring the localized semisolid zone during butt joining of Zamak-3 pressure die cast alloy is proposed and effect of welding parameters on mechanical and microstructural properties are investigated. A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately to create a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform joint. By presented process, globular microstructure of the weld zone is gained while the near weld zone would have the globular structure due to semisolid holding. Local mechanical properties of different zones show a good strength by results of the shear punch and hardness tests.