Microstructural Evolution during Partial Melting and Semisolid Forming Behaviors of Two Hot-Extruded Magnesium-Rare Earth Alloys

Jian-Sheng Zhang,Yao Tang,Jie Zhou,Qian Li,Yu-Feng Xia,Yi Meng,V.V Koryanov,H Yuan,M Polyakova

doi:10.1051/matecconf/201822001005

Jian-Sheng Zhang, Yao Tang + Show 7 more

Open Access

https://doi.org/10.1051/matecconf/201822001005

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Abstract

Reheating experiments and semisolid compression tests were conducted on two hot-extruded magnesium-rare earth (Mg-RE) alloys, Mg-8.20Gd-4.48Y-0.36Zr-3.34Zn and Mg-3.75Gd-5.15Y-0.75Zr-3.05Zn by using a multistage hot compression test machine. Dissolution of eutectic compounds, growth of grains, and partial melting took place during the reheating of these Mg-RE alloys and resulted in spherical semisolid slurries at certain temperatures (580 °C for Mg–8.20Gd–4.48Y–3.34Zn–0.36Zr, 560 °C for Mg-3.75Gd-5.15Y-0.75Zr-3.05Zn). Owing to the different alloying element contents of these two Mg-RE alloys, eutectic compounds with different morphologies were found inside them after reheating and rapid cooling processes. The forming characteristics of these two Mg-RE alloys in semisolid state were discussed based on the results of compression tests.

Highlights

Addition of Zr and rare earth (RE) elements was one of the most feasible precipitation strengthening methods for Mg alloys [1]
Block-shaped eutectic compounds with a large size and string-shaped eutectic compounds with a small size were observed in alloy B. In both alloys A and B, eutectic compounds were distributed parallel to the extrusion direction
The block- and stringshaped eutectic compounds in alloy B were both identified as Mg5(RE, Zn)

Summary

Introduction

Addition of Zr and rare earth (RE) elements was one of the most feasible precipitation strengthening methods for Mg alloys [1]. Casting was not an ideal forming process for Mg-RE alloys, because of the weaker mechanical properties of cast parts [4]. The formalities of Mg-RE alloys for traditional forging were not good enough to meet the requirement of near-shape forming [5]. The feasibility of semisolid forming in manufacturing of conventional Mg alloy parts was verified by in the past decade by researchers [7,8,9]. The research on semisolid forming of Mg-RE alloys is quite limited. To establish a feasible strategy for semisolid forming of Mg-RE alloys, essential acknowledgements should be obtained and accumulated by basic experiments

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