纳米多晶铝压缩塑性力学行为分子动力学研究  

Molecular Dynamics in Compressive Plastic Behavior of Nanocrystalline Aluminum

作　　者：张宇星 赵熹[1,2] 田学栋 张治民[1] ZHANG Yu-xing;ZHAO Xi;TIAN Xue-dong;ZHANG Zhi-min(School of Aeronautics and Astronautics,North University of China,Taiyuan 030051,China;National Defense Industry Innovation Center for Complex Component Extrusion Technology,North University of China,Taiyuan 030051,China)

机构地区：[1]中北大学航空宇航学院,太原030051 [2]中北大学国防科技工业复杂构件挤压成形技术创新中心,太原030051

出　　处：《精密成形工程》2023年第5期10-17,共8页Journal of Netshape Forming Engineering

基　　金：山西省高等学校创新人才支持计划;山西省科技合作交流专项(区域合作项目)(202104041101033)。

摘　　要：目的研究纳米多晶铝在不同温度与应变速率下的力学响应与塑性变形行为以及不同变形条件下的塑性力学行为。方法通过ATOMSK软件构建了晶粒取向随机的纳米多晶铝模型,利用LAMMPS软件在300~700 K温度以及1×10^(9)、5×10^(9)、1×10^(10)、1×10^(11)s^(-1)应变速率下完成了纳米多晶铝的压缩模拟,借助后处理OVITO软件对模拟结果进行了分析。结果随温度的升高,晶界原子所占比例增大,纳米多晶铝的弹性模量逐渐下降,在压缩过程中总位错密度随温度的升高而增大。随着应变速率的增大,材料硬化速率增加,纳米多晶铝表现出更高的屈服强度。当应变速率较低时,位错大量存在于小晶粒之中,且中央大晶粒相较于初始位置旋转了20°。当应变速率达到1×10^(11)s^(-1)时,材料的硬化速率极大提高,且在晶粒内部出现了孪晶。在塑性变形过程中,1/6<112>(不全位错)的数量最多,在位错运动中占主导地位。结论温度升高导致材料弹性模量降低,这主要是由于高温提供了更多能量,晶界原子占比增加。应变速率会影响纳米多晶铝的塑性变形方式,应变速率的增大使其由晶粒旋转变形转变为孪生变形与位错湮灭机制,导致纳米多晶铝硬化速率与屈服强度提高。The work aims to study the mechanical response and plastic deformation behavior of nanocrystalline aluminum under different temperature and strain rate compression conditions,as well as its plastic mechanical behavior under different deformation conditions.The nanocrystalline aluminum model with random grain orientation was constructed by ATOMSK.The compression of nanocrystalline aluminum at temperature of 300-700 K and strain rate of 1×10^(9),5×10^(9),1×10^(10)and 1×10^(11)s^(-1)was simulated by LAMMPS.The simulation results were analyzed by post-processing OVITO.With the increase of temperature,the proportion of grain boundary atoms increased,but the elastic modulus of nanocrystalline aluminum decreased,and the total dislocation density increased with the increase of temperature during compression.With the increase of strain rate,the hardening rate of the material increased,so the nanocrystalline aluminum presented higher yield strength.When the strain rate was low,a large number of dislocations existed in the small grains,and the central large grains rotated by 20°from the initial position.When the strain rate reached 1×10^(11)s^(-1),the hardening rate of the material was greatly improved,and twins appeared inside the grains.In the process of plastic deformation,the number of 1/6(incomplete dislocation)was the largest,which was dominant in dislocation motion.The main reason for the decrease of elastic modulus of material due to the increase of temperature is that high temperature provides more energy,leading to the increase of proportion of grain boundary atoms.Strain rate affects the plastic deformation mode of nanocrystalline aluminum.The increase of strain rate changes the deformation mode from grain rotation to twinning and dislocation,thus improving the hardening rate and yield strength of nanocrystalline aluminum.

关 键 词：纳米多晶铝 分子动力学 压缩 温度 应变速率 

分 类 号：TG146.21[一般工业技术—材料科学与工程]