纳米多晶Ni微观结构与力学性能的分子动力学模拟

Molecular dynamics simulation of microstructures and mechanical properties of nanocrystalline Ni

运用分子动力学技术,结合分析型嵌入原子方法(AEAM)模拟计算了平均晶粒尺寸为2.09～5.23nm的纳米多晶Ni的微观结构和力学性能。从原子能量分布、径向分布函数(RDF)、局域晶序结构的角度分析了纳米多晶Ni的晶界和晶粒结构,发现晶界部分所占的比例随晶粒尺寸的减小明显提高,结构与普通微晶的相似,纳米晶体的结合能较普通晶体的低。单向拉伸模拟结果表明:纳米多晶Ni的强度与晶粒尺寸之间出现反常Hall Petch关系;弹性模量的降低与纳米尺度结构特征相关。

The nanostructures and mechanical properties of nanocrystalline Ni with average grain size ranging from 2.09 nm to 5.23 nm were simulated with analytic embedded-atom method(AEAM) and Molecular Dynamics(MD). The grain boundary(GB) and nanocrystalline grain structure were analyzed with radial distribution function(RDF), energy analysis and common neighbor analysis(CAN) methods. The results indicate that the fraction of GB increases with the grain size decreasing and the GB structure is similar to that of the conventional coarse crystalline. The binding energy of nanocrystalline is lower than that of conventional microcrystal. Stress—strain curves show the reverse Hall-Petch relation in the present simulations. The decrease of elastic modulus is dependent on the nanostructure.