MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MAGNESIUM-ALUMINUM-MANGANESE CAST ALLOYS

Mg-Al-Mn (AM) based cast alloys were optimized for balanced tensile properties (strength and ductility) and response to heat treatment. The microstructure and mechanical property tests suggest that an aluminum content of 7-8% Al is optimum in these alloys for structural applications. AM80 (Mg-8%Al-0.3%Mn) alloy castings produced by super-vacuum die casting process show very good properties; yield strength of 157 MPa, ultimate tensile strength of 252 MPa and elongation of 5.6% in the as-cast condition, which compare favorably with the workhorse aluminum die casting alloy A380. Both T5 (artificial aging after as-cast condition) and T6 (artificial aging after solution and water quench) provided a similar improvement in strength for gravity-cast AM alloys containing more than 8% Al, but minimal strengthening in high pressure die castings.