Development of microstructure and mechanical properties of as cast Al–Mg–Mn alloy during high temperature ECAP

A large scale billet with diameter of 58.5 mm of an as cast Al-Mg-Mn alloy was processed by equal channel angular pressing (ECAP) at 350 degrees C up to six passes. A significant refinement of the grains was observed after six pressings to similar to 2 mu m. And the selected area electron diffraction (SAED) pattern showed that almost all of the grains were separated by boundaries with high angles of misorientation. A banded substructure was not observed during the hot ECAP, and a reasonably equiaxed structure was obtained just after one single pressing. Both the strength and the elongation increased abruptly in a single passage through the die, but thereafter, the increase was more gradual and exhibited a saturation effect after the fourth pressing. The good combination of strength and ductility of the Al-Mg-Mn alloy attained by the hot ECAP appeared to be attractive properties for industrial applications. Moreover, hot ECAP could possibly be used as an alternative step to hot extrusion or hot rolling in industrial processing, to break down an initial coarse as cast structure in a quite large scale billet.