Effect of minor Ca addition on microstructure and mechanical properties of a low-alloyed Mg-Al-Zn-Sn alloy

Due to the lack of secondary phases, low-alloyed Mg-Al series alloys usually exhibit low strength. In this work, by the addition of Ca element, a microstructure consists of a large fraction of fine recrystallized grains, profuse low angle boundaries and dense nano-sized CaMgSn particles has been achieved in a low-alloyed Mg-1.1Al-1.1Zn-0.2Sn-0.3Ca (wt%) alloy via sub-solidification followed by hot rolling and annealing. The addition of Ca in-troduces a large number of nano-sized CaMgSn particles, which can pin boundaries to inhibit recrystallization and grain growth during rolling and annealing. The annealed dilute Mg-1.1Al-1.1Zn-0.2Sn-0.3Ca alloy exhibits a high strength-ductility synergy with a yield strength (YS) of-249 +/- 3 MPa, an ultimate strength (UTS) of-308 +/- 4 MPa and a total elongation of-14 +/- 1.1%. The fine recrystallized grains and profuse low angle boundaries account mainly for the high YS, which contribute 65% to the total YS. Meanwhile, the precipitation strength-ening contributes-57 MPa to the total YS. The moderate elongation can be attributed to the activation of dislocations due to the fine grain sizes (-2 mu m), as well as Ca and Sn solute atoms in the alpha-Mg matrix. The present work provides an effective way to fabricate dilute Mg alloys with enhanced mechanical properties at room temperature by the combination of SRS, hot rolling and annealing.

Automated summary

By introducing Ca element, a microstructure consisting of fine recrystallized grains, low angle boundaries, and nano-sized CaMgSn particles has been achieved in a low-alloyed Mg-1.1Al-1.1Zn-0.2Sn-0.3Ca alloy. The addition of Ca inhibits recrystallization and grain growth during rolling and annealing. The annealed alloy exhibits high strength-ductility synergy, with a yield strength of -249 +/- 3 MPa, an ultimate strength of -308 +/- 4 MPa, and a total elongation of -14 +/- 1.1%.