[110], [112], [111]晶向钨纳米线拉伸微结构演变

采用嵌入原子势,使用分子动力学方法,模拟研究了110]、112]和111]三个晶向钨纳米线的拉伸弛豫过程的微观破坏机理.并引入共近邻分析方法、配位数及中心对称参数法来分析它的结构和形状的演化过程.结果表明:不同晶向的纳米线拉伸时具有不同的力学性能,111]晶向具有最大的弹性模量、屈服应变、屈服强度与断裂应变,其次是110]晶向,最后是112]晶向.晶向对弹性模量的影响较小,但对屈服应变、屈服强度、断裂应变影响较大.模拟结果还表明:这三个晶向均具有弹性、损伤、屈服及颈缩断裂四个阶段,且发现112]晶向具有强化阶段,即应力随应变的增加而增加,重新恢复承载能力,但其断裂应变最小.并给出了这三种不同晶向拉伸断裂的机理.

Microstructure evolution on tensile of tungsten nanowires with different crystal orientations of [110], [112] and [111]

Mechanical properties and micro-structure fracture mechanism of tungsten nanowires with crystal orientation of 110],112] and 111] have been investigated with molecular dynamics and embedded atom methods. Simultaneously common neighbor analysis, center symmetry parameters and coordination number has been employed to analysis the evolution of structure. It is concluded that different crystal orientation nanowires have different characters. The elastic modulus, yield strain, yield strength and the fracture stress is decreasing in the sequence of111], 110]and 112] crystal orientations. It also reveal that all of the stress-strain curves are classified into four stages: elastic stage, damage stage, yielding stage and failure stage. It concluded that crystal orientation has slightly impact on the elastic modulus but has great effect on tensile strength, yield strength and ductility. Interestingly, hardening stage has been found in tungsten nanowire with crystal orientation of 112] at yielding stage. That is to say the strain increase with the stess increase in the hardening stage, the nanowire with crystal orientation of 112] has the trend that recover its capability in strength, but consequently result in the least ductility. In the end the tensile failure mechanisms of the three nanowires have been summarized. Key Words: molecular dynamics; stress−strain curve; tungsten nanowire; crystal orientation