Wu Cheng-Da, Tsai Hsing-Wei
Department of Mechanical Engineering, Chung Yuan Christian University, 200, Chung Pei Rd., Chung Li District, Taoyuan City, 32023, Taiwan.
J Mol Model. 2017 Apr;23(4):114. doi: 10.1007/s00894-017-3295-y. Epub 2017 Mar 13.
The effect of notch size (r) on nanocrystalline (NC) and single-crystal (SC) Au at a temperature of 300 K under tension testing is studied using molecular dynamics simulations based on the many-body embedded-atom potential. The effect is investigated in terms of atomic trajectories, common neighbor analysis, and the stress-strain curve. The simulation results show that for the NC samples, stacking faults nucleate at grain boundaries (GBs), propagate inside grains, and eventually are terminated by GBs or transect them. For tensile-deformed NC and SC samples with larger r values, necking and breaking occur faster, which indicates that ductility decreases. SC samples exhibit larger yield strength and ultimate strength than those of NC samples. SC samples have a longer elastic deformation period due to their lack of GBs. For NC samples, increasing the r value increases Young's modulus but decreases the yield point; in addition, it decreases mechanical strength and speeds up the formation of necking.
基于多体嵌入原子势的分子动力学模拟，研究了在300K温度下拉伸试验中，缺口尺寸（r）对纳米晶（NC）和单晶（SC）金的影响。从原子轨迹、共同邻域分析和应力-应变曲线方面对该影响进行了研究。模拟结果表明，对于NC样品，堆垛层错在晶界（GBs）处形核，在晶粒内部扩展，最终被GBs终止或横穿GBs。对于具有较大r值的拉伸变形NC和SC样品，颈缩和断裂发生得更快，这表明延展性降低。SC样品比NC样品表现出更大的屈服强度和极限强度。由于缺乏GBs，SC样品具有更长的弹性变形期。对于NC样品，增加r值会提高杨氏模量，但会降低屈服点；此外，它会降低机械强度并加速颈缩的形成。
