In this study, the effect of Zn and Ca addition on microstructure and strength at room temperature of Mg-Sn alloys was investigated by comparison of Mg-6Sn, Mg-6Sn-2Zn, and Mg-6Sn-2Zn-1Ca alloys in as-cast and as-extruded states. In the as-cast samples, α-Mg and Mg₂Sn phases were the main phases of Mg-6Sn and Mg-6Sn-2Zn alloys, while the CaMgSn phase was formed in Mg-6Sn-2Zn-1Ca alloy due to the addition of the Ca element. Mg₂Sn phase dissolved into the matrix during homogenization while CaMgSn phase remained. Incomplete dynamic recrystallization (DRX) took place in these alloys during hot extrusion. Fine Mg₂Sn precipitates were observed in α-Mg matrix of as-extruded samples. Zn showed little influence on microstructure, whereas Ca reduced the volume fraction of un-DRXed grains and increased the size of DRXed grains. As-extruded Mg-Sn alloys exhibited typical fiber texture. The strength at room temperature of Mg-Sn alloys improved significantly after hot extrusion. The addition of Zn element was beneficial to the strength at room temperature of the Mg-6Sn alloy, while the further addition of Ca element was harmful to the strength. Among these alloys, the Mg-6Sn-2Zn alloy exhibited the best strength at room temperature in both as-cast and as-extruded states.

The microstructure and mechanical properties of magnesium (Mg) alloys are significantly influenced by the casting process. In this paper, a comparative study on microstructure and mechanical properties at ambient and elevated temperatures of AZ91-2wt.% Ca (AZX912) Mg alloy samples prepared by gravity casting (GC), squeeze casting (SC) and rheo-squeeze casting (RSC), respectively, was carried out. The results show that α-Mg grains in SC and RSC samples are significantly refined compared to the GC sample. The average secondary dendritic arm spacing of AZX912 alloy samples decreases in the order of GC, SC and RSC. As testing temperature increases from 25 °C to 200 °C, strength of AZX912 alloy samples is reduced, while their elongation is increased continuously. Compared to GC and SC processes, RSC process can improve the mechanical properties of AZX912 alloy at both ambient and elevated temperatures. The enhancement of mechanical properties of RSC sample over GC and SC samples mainly results from grain refinement in the as-cast microstructure of AZX912 alloy.

In this study, as-cast Mg–6Sn–2Zn (wt.%) alloy was subjected to friction stir processing (FSP) and the microstructure and tensile properties of FSP Mg–6Sn–2Zn samples were investigated. It was found that, in the stir zone (SZ) of FSP Mg–6Sn–2Zn samples, α-Mg grains were significantly refined via dynamic recrystallization (DRX) and the Mg₂Sn phase was broken and partially dissolved. The microstructure in SZ was nonuniform and DRXed grains in the SZ-up regions were coarser than those in the SZ-down regions. Coarse broken Mg₂Sn particles were observed in the SZ-up regions, while only fine Mg₂Sn particles were observed in the SZ-down regions. Strong {0001} basal texture developed in the SZ regions of Mg–6Sn–2Zn samples after FSP. The increase of travel speed had little effect on the texture of different SZ regions. The ductility of FSP Mg–6Sn–2Zn samples was obviously improved, while the improvement in strength was negligible when compared to the as-cast sample. The tensile properties of FSP Mg–6Sn–2Zn samples were influenced by grain refinement, texture modification, and the breaking up and dissolution of the Mg₂Sn phase.

In this study, as-cast Mg-6 wt % Sn alloy is subjected to one-pass and two-pass friction stir processing (FSP). The effect of processing pass on microstructure and mechanical properties of FSP Mg-6Sn alloy is investigated. It is found that one-pass FSP leads to the breakage and partial dissolution of the Mg₂Sn phase in the stir zone (SZ) and two-pass FSP leads to the further dissolution and dynamic precipitation of the Mg₂Sn phase. Dynamic recrystallization (DRX) takes place in the SZ of an Mg-6Sn alloy undergoing FSP. Compared to one-pass FSP, two-pass FSP brings about further grain refinement in the SZ. A strong {0001} basal texture is developed in the SZ of a Mg-6Sn alloy from FSP and the change of the sample region or processing pass has little influence on the texture. Compared to an as-cast Mg-6Sn sample, one-pass FSP brings about significant improvement in mechanical properties. Two-pass FSP leads to the further increase in yield strength (YS) and ultimate tensile strength (UTS) but elongation (EL) is reduced. The continuous increase in strength is attributed to the grain refinement and the dissolution and dynamic precipitation of Mg₂Sn phase achieved by FSP.