纳米多晶Mg-Y合金压缩力学行为的分子动力学研究

Molecular Dynamics of the Compressive Mechanical Behavior of Nanopolycrystalline Mg-Y Alloy

目的研究纳米多晶Mg-Y合金在不同温度和应变速率下的力学响应以及不同变形条件下的晶粒变形行为。方法通过ATOMSK软件构建了晶粒取向随机的纳米多晶Mg-Y二元合金模型,利用LAMMPS软件,在400~520 K温度及1×10^(10)s^(−1)、1×10^(9)s^(−1)应变速率下完成了纳米多晶Mg-Y合金的压缩模拟,借助后处理OVITO软件对模拟结果进行了分析。结果随着温度的升高,纳米多晶Mg-Y合金的力学性能降低,且在温度上升到一定程度后具有一定的梯度规律。在微观层面,温度的上升使总体位错密度下降,但减少了晶粒内部的长程位错和位错扭结,并且<c+a>类位错与类位错的比例上升。纳米多晶Mg-Y合金在高应变速率下的屈服强度更高,在原子排布层面上,六方最密堆积的比例降低。结论温度升高带来的更多能量使低能态的Y原子更容易参与到位错产生、消失过程中,还加剧了<c+a>类型位错向类位错的转变。高应变速率通过大幅度转化基体Mg的六方最密堆积形式,增加了晶界的破碎和形核,影响了合金的力学性能。

The work aims to study the mechanical response of the nanopolycrystalline Mg-Y alloy at different temperature and strain rates and the grain deformation behavior under different deformation conditions.The nanopolycrystalline Mg-Y alloy model with random grain orientation was constructed by ATOMSK software,and the compression simulation of nanopolycrys-talline Mg-Y alloy at the temperature of 400-520 K and strain rates of 1×10^(10)s^(−1)and 1×10^(9)s^(−1)was completed by LAMMPS software.The simulation results were analyzed by post-processing software OVITO.With the increase of temperature,the me-chanical properties of nanopolycrystalline Mg-Y alloy decreased and had a certain gradient law after the temperature rose to a certain extent.At the microscopic level,the rise in temperature caused a decrease in the overall dislocation density,but alleviated the generation of long-range dislocation and kinink within the grain,and the proportion of<c+a>todislocation increased.The nanopolycrystalline Mg-Y alloy had higher yield strength at high strain rates and decreased the ratio of the closest hexago-nal packing at the atomic arrangement level.The more energy brought by the temperature increase makes it easier for Y atoms to participate in the process of misgeneration and disappearance,and also causes the transition of<c+a>to.The high strain rate increases the fragmentation and nucleation of the grain boundary by substantially converting the hexagonal closest packing form of the matrix Mg,and affects the mechanical properties of the alloy.