摘要
This work investigated the effects of different Y additions(0,1.5,3.0 and 4.5 wt.%)on the microstructural evolution and mechanical performance of cast Mg−3Nd−0.2Zn−0.5Zr alloy.The results show that as the Y content increases,the key secondary phases in as-cast alloys change from the Mg_(12)Nd type to the Mg_(24)Y_(5) type.Meanwhile,the number density of Zn−Zr particles in the grains of as-quenched alloys gradually decreases.HAADF-STEM observations of peak-aged samples reveal that element Y is greatly enriched in the globularβ¢precipitates,leading to a significantly increased volume fraction and promoted precipitation kinetics ofβ¢precipitates,resulting in enhanced strength of the alloy.Tensile tests reveal that,with the addition of 4.5 wt.%Y,the yield strength of the base alloy is substantially increased by 88 and 61 MPa after being aged at 200 and 225°C under peak-aged conditions,respectively.
研究不同Y添加量(0、1.5%、3%和4.5%,质量分数)对铸造Mg−3Nd−0.2Zn−0.5Zr合金显微组织演变及力学性能的影响规律。结果表明,随着Y含量的增加,铸态合金中主要的第二相由Mg_(12)Nd型逐步转变为Mg_(24)Y_(5)型。同时,固溶态合金中的Zn−Zr相的数量随着Y含量的增加逐渐减少。利用HAADF-STEM技术观察到峰时效状态下Y元素在球状柱面β′相中显著富集。随着Y含量的增加,峰时效状态下合金中β′的体积分数显著增大。由于Y元素的加入,β′相析出动力显著增大,进而使得合金强度得到显著提高。拉伸试验结果表明,当Y添加量为4.5%(质量分数)时,在200和225℃峰值时效条件下合金屈服强度增量分别为88和61 MPa。
基金
supported by the National Natural Science Foundation of China(Nos.U2037601,51775334 and 51821001)
the National Key Research&Development Program of China(No.2016YFB0701205)
the Joint Innovation Fund of CALT and College,China(No.CALT2020-TS07)
the Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment,China(No.SKL2020005)
the Research Program of Joint Research Center of Advanced Spaceflight Technologies,China(No.USCAST2020-14).
