A simulation study of the shape of β′ precipitates in Mg-Y and Mg-Gd alloys
A simulation study of the shape of β′ precipitates in Mg-Y and Mg-Gd alloys
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DOI：
10.1016/j.actamat.2012.09.044
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发表时间：
2013-01-01
期刊：
影响因子：
9.4
通讯作者：
Nie, J. F.
中科院分区：
文献类型：
--
作者：
Liu, H.;Gao, Y.;Nie, J. F.
亚稳β '相是Mg-RE（RE：稀土元素）基合金中的关键强化沉淀相。β '相的形貌由Mg-Y合金中的小面状和近等轴状转变为Mg-Gd合金中的截头透镜状。本文采用第一性原理计算和相场模拟相结合的方法，研究了界面能和共格弹性应变能对Mg-Y和Mg-Gd二元合金中β '相析出形貌的影响。在没有任何自由拟合参数的情况下，使用第一性原理计算、CALPHAD数据库和实验表征作为模型输入（β '相的晶格参数、Mg基体的弹性常数和化学自由能以及共格β'/Mg基体界面的界面能），相场模拟预测了不同尺寸的β '沉淀物的平衡形状，与实验观察吻合得很好。分析了引起β ′-Mg_7 Y和β ′-Mg_7 Gd析出相平衡形状差异的因素，讨论了提高β ′相长径比从而提高Mg-RE合金强度的可能途径。(c)2012 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The metastable beta' phase is a key strengthening precipitate phase in a range of Mg-RE (RE: rare-earth elements) based alloys. The morphology of the beta' precipitates changes from a faceted and nearly equiaxed shape in Mg-Y alloys to a truncated lenticular shape in Mg-Gd alloys. In this work, we study effects of interfacial energy and coherency elastic strain energy on the morphology of beta' precipitates in binary Mg-Y and Mg-Gd alloys using a combination of first-principles calculations and phase-field simulations. Without any free-fitting parameters and using the first-principles calculations, CALPHAD databases and experimental characterizations as model inputs (lattice parameters of the beta' phase, elastic constants and chemical free energy of Mg matrix and interfacial energies of the coherent beta'/Mg matrix interfaces), the phase-field simulations predict equilibrium shapes of beta' precipitates of different sizes that agree well with experimental observations. Factors causing the difference in the equilibrium shape of beta'-Mg7Y and beta'-Mg7Gd precipitates are identified, and possible approaches to increase the aspect ratio of the beta' precipitates and thus to enhance the strength of Mg-RE alloys are discussed. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.