Growth kinetics of Al-Mg intermetallics during post-weld annealing treatment

We explored the growth kinetics of intermetallic compound (IMC) layers at the joint interface of the friction stir lap welded Mg alloy to Al alloy joint during post-weld annealing treatment. The intermetallic layer formed between the Al alloy and Mg alloy was composed of continuous beta phase and gamma phase; the beta phase layer grows faster than the gamma phase layer. A quantitative analysis of the IMC layer thickness as a function of aging time and temperature was performed. The diffusion coefficients were calculated from the parabolic relationship between the migration of the interface and the annealing time. The activation energies for IMC growth were determined as 113.5 and 69.3 kJ mol(-1) for the gamma and beta phases, respectively.