Improvements in strength and microstructural behaviour of friction stir welded 7475 aluminium alloy using in-process cooling

Al-Zn-Mg alloys are considered difficult to weld using fusion welding techniques. In the present study AA7475 has been welded with in-process cooling using two different cooling conditions. The mechanical properties have been carefully examined along with the micro-structural evolution. Improvements in the mechanical properties were observed. It was found that severe plastic deformation and in-process cooling resulted in extremely fine grains in the SZ region. Extremely good microstructural stability was observed in each of the samples especially ice water slush. Cooling has resulted in exceptional mechanical properties and hardness in the welds. The welds were characterized using SEM and EDX was also done on each of the samples. EDX data revealed high density of strengthening precipitates in the boundaries of the TMAZ and SZ. It also revealed high weight density of Mg along the zone interfaces.