Effects of Sn addition on the microstructure and mechanical properties of as-cast, rolled and annealed Mg-4Zn alloys

The effects of Sn addition on the microstructure and mechanical properties of as-cast, as rolled and subsequent isothermal annealed Mg-4Zn alloys are investigated. Tensile and Rockwell hardness tests are conducted to evaluate the mechanical properties of the as-cast alloys. Improvements of the mechanical properties in Sn-containing alloys are attributed to the increasing volume fraction of secondary phases and modifying the type of intermetallic phases. Additions of Sn increase the twinning density and modify the annealing texture in as-rolled Mg-4Zn alloys. In comparing rolled-annealed Mg-4Zn to Mg-4Zn-3Sn alloy, numerous small particles are dispersed in the matrix of rolled-annealed Mg-4Zn-3Sn alloy. The particles exhibit two different morphologies and sizes: nanosized Zn-rich particles and rectangular-shaped Mg2Sn particles with a size of about 175 nm. The rolled-annealed Mg-4Zn-3Sn alloy exhibits high ultimate tensile strength, yield strength and elongation of 273 MPa, 159 MPa and 16.2%, respectively. The UTS and YS are about 16% and 53% higher than Sn-free alloy.