Microstructure and mechanical properties of Mg–3.0Y–2.5Nd–1.0Gd–x Zn–0.5Zr alloys produced by metallic and sand mold casting

Abstract

Mg–3.0Y–2.5Nd–1.0Gd–x Zn–0.5Zr (x = 0, 0.2, 0.5, and 1.0) (wt%) alloys were produced by metallic and sand mold casting to study the microstructure and mechanical properties of the alloys. The as-cast Zn-free alloys consist of α-Mg and eutectics, whereas the Zn-containing alloys contain additional long-period stacking ordered (LPSO) structures. With a higher solidification, the cooling rate brought by metallic mold casting, grains, and eutectics are refined, which enhances the elongation of the alloys, accompanied by a decrease of area fraction of the LPSO structure. Some residual eutectics in the Mg–3.0Y–2.5Nd–1.0Gd–1.0Zn–0.5Zr alloys act as obstacles to grain boundary migration during solution treatment, which make the average grain size 15–20 μm smaller than that of the other alloys and hence improve the elongation of the alloys. The Zn addition brings notable enhancements to mechanical properties of the alloys due to solid solution strengthening of Zn. Especially, the peak-aged Mg–3.0Y–2.5Nd–1.0Gd–0.5Zn–0.5Zr alloys perform with the highest overall tensile properties.

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ACKNOWLEDGMENTS

This work is supported by National Key Research and Development Program of China (No. 2016YFB0301003); Shanghai Yang-fan Program (No. 14YF1402000), National Natural Science Foundation of China (No. 51404153); Research Program of Joint Research Center of Advanced Spaceflight Technologies (No. USCAST2015-25); and Science Innovation Foundation of Shanghai Academy of Spaceflight Technology (Nos. SAST2015047 and SAST2016048).

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Correspondence to Liang Zhang.

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Zhang, H., Zhang, L., Wu, G. et al. Microstructure and mechanical properties of Mg–3.0Y–2.5Nd–1.0Gd–x Zn–0.5Zr alloys produced by metallic and sand mold casting. Journal of Materials Research 32, 3191–3201 (2017). https://doi.org/10.1557/jmr.2017.302

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