Fundamental Physical Metallurgy Background for FSW/P

Abstract

All metal processing activities involve a combination of deformation and heat transfer where depending on the processing path a variation in microstructure occurs. For a thermo-mechanical process like FSP, variations in process parameters are accompanied by changes in deformation and heat transfer characteristic with consequent variations in the microstructure. In Fig. 3.1a, b the microstructure of an Al alloy (Al-Mg-Si type) obtained through two different casting routes are shown while Fig. 3.1c, d presents the differences in welded macrostructure of a AA356 alloy using the same FSW tool at different operating parameters. As is evident, depending on the processing conditions the microstructure differs drastically with consequent changes on the macrostructure.