纳米晶钽在单向拉伸载荷下的分子动力学模拟

利用分子动力学方法模拟了纳米晶钽在单轴拉伸载荷作用下的微观结构演化情况. 结果表明纳米晶钽在塑性变形过程中可以发生从BCC到FCC, HCP结构的应力诱导相变. FCC 结构原子百分比的最大值和试样的抗拉强度成线性关系，据此可推出一个相变发生的临界应 力值. 应变率越大，相变滞后于应力越严重. 当应变达到一定值时，试样会发生晶间断裂现 象，定量分析发现纳米晶钽晶间裂纹初始形成应变不受平均晶粒尺寸的影响，而与应变率和 模拟温度有着密切的关系.

MOLECULAR DYNAMICS SIMULATIONS OF NANOCRYSTALLINE Ta DURING UNIAXIAL TENSILE DEFORMATION PROCESS

Using molecular dynamics simulations, the microstructure evolution of nanocrystalline Ta under uniaxial tensile loading is investigated. The results show that stress-induced phase transitions from BCC to FCC and HCP structures may take place during the deformation process. The maximum of the fraction of FCC atoms varies with the tensile strength linearly, by which we can find a critical stress when the phase transition takes place. The higher the strain rate is, the later the phase transition occurs. Intergranular fracture is also found during the deformation process. Crack-formation strain is influenced not by the mean grain size, but also by the strain rate and the simulation temperature.