拉伸速率对含缺陷单晶镁塑性变形机制的影响

Effect of tensile rate on plastic deformation mechanism of single crystal magnesium containing defects

运用嵌入式原子势函数对同时存在微裂纹和孔洞缺陷的单晶镁在不同拉伸速率下的塑性变形行为进行了分子动力学模拟。结果表明,材料的杨氏模量与拉伸速率关联不大,屈服应力随拉伸速率的增加而增大。拉伸速率越大,体系总能量增加越多,峰值也越高,材料屈服强度越大。不同拉伸速率下材料的塑性变形机制不同,当拉伸速率较低时,主裂纹扩展并与预设孔洞汇合,裂纹继续扩展直至材料断裂失效。当拉伸速率较高时,主裂纹裂尖变钝,模型右下方产生边缘裂纹加速材料断裂失效。塑性变形机制的主要形式包括位错形核、位错发射、原子滑移和原子相变,其中位错发射和原子滑移起主导作用。

The molecular dynamics simulation of plastic deformation behavior of single crystal magnesium with microcracks and voids with different tensile rates was carried out using the embedded atomic potential function.The results show that the tensile rate has little correlation with Young′s modulus and the yield stress increases with the increase of tensile rate.The higher the tensile rate is,the more the total energy of the system increases,the higher the peak value is,and the greater the yield strength of the material is.The plastic deformation mechanism of the material is different with different tensile rates.When the tensile rate is low,the main crack expands and joins with the preset hole,and the crack continues to expand until the material fracture is ailure.When the tensile rate is high,the crack tip of the main crack becomes blunt and the edge crack appears at the bottom right of the model to accelerate the fracture failure of material.The main forms of plastic deformation mechanism include dislocation nucleation,dislocation emission,atomic slip and atomic phase transformation,among which dislocation emission and atomic slip play a leading role.