Abstract
The microstructure and Gd-rich phase evolution of as-cast AZ31-xGd (x=0, 1.5 wt.%, 2.0 wt.% and 2.5 wt.%) magnesium alloys during semi-solid isothermal heat treatment were investigated deeply in the present work. Results showed that the lamellar (Mg,Al)3Gd phases transformed into the particle-like Al2Gd phases in AZ31 magnesium alloys with Gd addition during semi-solid isothermal heat treatment, leading to yielding more spherical α-Mg grains. When Gd content is 2.0 wt. %, the size of semi-solid spherical grains reaches the minimum. The main mechanism of grain refinement lies in the remelting of dendritic branches as well as the auxiliary effect of a small number of Al2Gd particles as grain refining inoculants. Meanwhile, Al2Gd particles enriched at the solid-liquid interfaces can remarkably retard the growth rate of α-Mg grains. A reduction of deformation resistance has been successfully achieved in AZ31-2.0Gd magnesium alloy after semi-solid isothermal heat treatment, which shows a moderate compressive deformation resistance (230 MPa), comparing to the as-cast AZ31 magnesium alloy (280 MPa) and semi-solid AZ31 magnesium alloy (209 MPa).
摘要
本文深入研究了铸态 AZ31-xGd (x=0, 1.5 wt%, 2.0 wt%, 2.5 wt%) 镁合金在半固态等温热处理中显微组织和富 Gd 相的演变。 结果表明, 添加 Gd 的 AZ31 镁合金中的层状 (Mg,Al)3Gd 相在半固态等温热处理过程中转变为颗粒状 Al2Gd 相, 导致形成更多的球状 α-Mg 晶粒。 当 Gd 含量为 2.0% (质量分数)时, 半固态球状晶粒的尺寸达到最小值。 晶粒细化的主要机理在于树枝晶的重熔以及少量充当孕育剂的 Al2Gd 相的辅助作用。 同时, 固液界面处富集的 Al2Gd 颗粒可以显著阻碍 α-Mg 晶粒的粗化长大。 与铸态 AZ31 镁合金(280 MPa)和半固态 AZ31 镁合金(209 MPa)相比, 经过等温, 处理的半固态 AZ31-2.0Gd 镁合金具有适中的压缩变形抗力(230 MPa), 实现了变形阻力的降低。
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CHU Chen-liang performed the data analyses and wrote the manuscript; YAN Hong and LUO Chao helped perform the analysis with constructive discussions; TANG Bin-bing helped with the TEM analysis; WU Xiao-quan and QIU Shui-cai played an important role in interpreting the results; YIN Zheng contributed significantly to manuscript preparation; HU Zhi contributed to the conception of the study.
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Project(20171BAB206005) supported by the Natural Science Foundation of Jiangxi Province, China; Project(20153BCB23023) supported by the Training Program Foundation for Young Scientists of Jiangxi Province, China; Project(51961026) supported by the National Natural Science Foundation of China
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Chu, Cl., Wu, Xq., Qiu, Sc. et al. Microstructure and Gd-rich phase evolution of as-cast AZ31-xGd magnesium alloys during semi-solid isothermal heat treatment. J. Cent. South Univ. 28, 1–15 (2021). https://doi.org/10.1007/s11771-020-4504-x
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DOI: https://doi.org/10.1007/s11771-020-4504-x