Structure and properties of ultrafine-grained Al-Zn-Mg-Cu and Al-Cu-Mg-Mn alloys fabricated by ECA pressing combined with thermal treatment

An investigation was conducted on the structures and properties of aluminum-based alloys 7050 and 2224 with submicrocrystalline grains produced by severe plastic deformation through equal-channel angular pressing (ECA pressing). Special attention was paid to how the heat treatments before or after ECA pressing affected the structures and properties of alloys 7050 and 2224. The results showed that the ultimate tensile strength (UTS) of alloy 7050 reached 677 MPa, with elongation to failure of 15%, while the UTS of alloy 2224 reached 618 MPa, with elongation to failure of 12%. The forming of finer grains after ECA pressing resulted from cutting off shearing bands directly and from recrystallization at certain strain and annealing regimes. In this paper, three strengthening mechanisms were considered: grain refinement strengthening, high dislocation strengthening, and more homogenous and finer precipitations than the conventional T6-treated alloy.