Abstract: A new wrought magnesium sheet alloy, the Mg-3Al-1Sn alloy (AT31) with both high strength and high ductility, was obtained by first extrusion and subsequent single-pass large-strain rolling processing. The microstructure analysis showed that the certain amounts of Mg₁₇Al₁₂ phases and Mg₂Sn phases were precipitated in the AT31 alloy, and the grains of the as-extruded alloys were effectively refined after rolling, and the strength was significantly improved. After low-temperature rolling at 250℃, the most obvious grain size refinement is detected in the AT31 alloy. The grain size was reduced to be about 4.72 μm after a single pass of about 58% deformation. As the deformation is increased to about 66%, the grain size of the AT31 alloy slightly grows, about 4.94 μm. After rolling at 300℃, the minimum grain size can reach about 5.58 μm. Similarly, with the amount of deformation increasing, the grain size significantly decreases firstly and then increases. The grain size change is in accordance with the variation of yield strength, which further corresponds to the classical grain refinement hardening theory. The Mg-3Al-1Sn alloy sheet which is rolled by a single pass to about 58% at 250℃, exhibits the optimal combination of tensile strength and elongation. The yield strength, the ultimate strength and the elongation of as-rolled AT31 alloy are about 185 MPa, about 256 MPa, about 29.2%, respectively. Therefore, Mg-Al-Sn alloy has a broad application potential in the industry.

Key words: magnesium alloy, rolling deformation, dynamic recrystallization, second phase, grain refinement