Effects of heat treatment on microstructure and mechanical properties of Mg-2.6Sm-1.3Gd-0.6Zn-0.5Zr alloy

The microstructure and mechanical properties of as cast and different heat treated Mg-2.6Sm1-3Gd-0.6Zn-0.5Zr (wt-%) alloy were investigated. The alloy in the as cast state is mainly composed of alpha-Mg matrix and (Mg, Zn)(3)(Sm, Gd)(1) eutectic compounds. After solution treatment at 510 degrees C for 4 h, the eutectic compound dissolved into the matrix completely. A good combination of tensile strength and ductility was obtained when the alloy was aged at 200 degrees C for 32 h; the ultimate tensile strength, yield strength and elongation are 282 MPa, 185 MPa and 6.1% respectively. Precipitation strengthening is the largest contributor to strength (similar to 67%) in 200 degrees C peak aged alloy, which is related to plate shaped precipitate phases formed on prismatic planes of the alpha-Mg matrix.