采用分子动力学(MD)方法对纳米单晶氩杆进行了机械拉伸变形和断裂的模拟研究.在拉伸过程中可以观察到原子位错,间隙的形成,裂纹的出现,以及后来的断裂分离等现象,与宏观的拉伸试样相似.MD模拟的拉伸试样的真实应力应变图显示,纳米单晶氩杆随着应变的增加应力略有增加,超过某一应变值后,应力急剧增加到最大值.随后,在加载速率较大时试样突然脆性断裂,在加载速率较小时应力却有一个突然的下降变负过程.这说明加载速率对材料的强度影响很大,当加载速度分别为2.16m/s和6.49m/s时,纳米单晶氩材料相应的断裂强度为2.6GPa和6.6GPa.纳米单晶氩材料在断裂前经历了一个较大的塑性变形过程,但其断裂方式却是完全脆性的.另外,纳米单晶氩材料在自由边界条件下充分弛豫后在垂直于拉伸的方向有轻微的收缩,不同于Al,Cu,Ni等具有FCC晶格结构的纳米单晶材料由于内力的作用引起轻微膨胀.
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