Microstructure Evolution During Fusion Welding of Rheocast AA7075 Alloy

The microstructural evolution during varying thermal gradients of rheocast AA7075 aluminium alloy was investigated. To perform this study, semi-solid billets of non-dendritic microstructure were produced using Linear Electro Magnetic Stirrer (LEMS). Gas Tungsten arc welding (GTAW) was conducted to simulate varying thermal gradients near fusion zone. Welding simulations were performed using SYSWELD®. Quantitative metallography was used to aid the analysis. Numerical simulations and quantitative results show that the width of the partially melted zone (PMZ) plays a vital role in the nucleation mechanism and dendritic microstructure formation in this class of alloys.