Improvement in Mechanical Properties of Rolled AZ31 Alloy Through Combined Addition of Ca and Gd
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Improvement in Mechanical Properties of Rolled AZ31 Alloy Through Combined Addition of Ca and Gd Jongbin Go1 · Jong Un Lee1 · Byoung Gi Moon2 · Jonghun Yoon3 · Sung Hyuk Park1 Received: 1 October 2019 / Accepted: 18 December 2019 © The Korean Institute of Metals and Materials 2020
Abstract In this study, the effects of the combined addition of Ca and Gd on the microstructure and mechanical properties of rolled Mg alloys are investigated by the addition of 0.5 wt% Ca and 0.5 wt% Gd to a commercial AZ31 alloy. The combined addition of Ca and Gd leads to the formation of undissolved second phases such as A l2Ca and A l2Gd, which promote dynamic recrystallization during rolling via the particle-stimulated nucleation phenomenon. As a result, the rolled AZ31–0.5Ca– 0.5Gd (wt%) (AZXG3100) alloy shows a finer recrystallized grain structure than the rolled AZ31 alloy; the average grain size of the former (11.9 µm) is considerably smaller than that of the latter (22.4 µm). The combined addition of Ca and Gd improves the tensile yield strength of the rolled material from 131 to 144 MPa, which is attributed mainly to the combined effects of Hall–Petch hardening enhanced by grain refinement and dispersion hardening induced by the undissolved particles. The tensile elongation of the rolled material also increases from 14.6 to 18.3% upon the combined addition of Ca and Gd, because the activation of twinning during tension is less pronounced in the rolled AZXG3100 alloy owing to its smaller grain size. These results demonstrate that the combined addition of Ca and Gd simultaneously improves the tensile strength and ductility of the rolled AZ31 alloy. Keywords Magnesium · Ca and Gd addition · Rolling · Microstructure · Mechanical properties
1 Introduction With the gradual tightening of regulations on the carbon dioxide emissions and fuel efficiency of automobiles, Mg alloys—on account of their low density and high specific strength—have attracted considerable attention in the automobile industry for the purpose of vehicle weight reduction [1–4]. Because of their superior castability, Mg alloys have mostly been applied to automotive components in the form of cast materials [5]. However, development of wrought Mg alloys possessing excellent mechanical properties is necessary for expanding the application range of Mg alloys. Rolled materials have been widely used in various industries * Sung Hyuk Park [email protected] 1
School of Materials Science and Engineering, Kyungpook National University, Daegu 41566, Republic of Korea
2
Implementation Research Division, Korea Institute of Materials Science, Changwon 51508, Republic of Korea
3
Department of Mechanical Engineering, Hanyang University, Ansan 15588, Republic of Korea
because of the high productivity of the rolling process and the good mechanical properties of rolled products. However, rolled Mg alloys, having a hexagonal close-packed lattice structure, exhibit poor ductility and formability at room temperature (RT) owing to the lack of active slip systems [6
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