Dynamic recrystallization in Al–Mg–Sc alloys

The main research interest was to investigate the mechanisms in the restoration process of Al–3 mass% Mg and Al–3 mass% Mg–0.2 mass% Sc alloy containing second-phase Al3Sc precipitates. The alloy specimen, Al–3% Mg–0.2% Sc, was peak-aged, where it contained stable coherent, spherical Al3Sc precipitates with an average diameter of 0.2 μm and a volume fraction of 0.005. The main techniques utilized are compression tests, optical microscopy, the Laue X-ray method, the electron backscattering pattern method using a scanning electron microscopy and transmission electron microscopy (TEM). The observed fluctuation of the stress–strain curves and grain growth during high temperature deformation strongly suggested the occurrence of dynamic recrystallization during hot deformation of the alloy. The transmission Laue method revealed new undeformed spots formed during deformation, which directly shows that new grains have been generated. TEM observation revealed the areas of high dislocation density at the immediate vicinity of the particles in hot deformed conditions. In the ternary alloy (Al–3% Mg–0.2% Sc), dynamic recrystallization seems to occur more frequently than in the binary alloys (Al–3% Mg) through grain boundary bulging. These observations lead to a hypothesis that dynamically recrystallized grains in the present study were nucleated by the combined effects of stress induced grain boundary bulging and preferential hardening at the sites of Al3Sc precipitates near grain boundaries.