拉伸载荷下α-Ti孔洞生长的机制研究

Expansion Mechanism of Vacancy inα-Ti under Tensile Loading

利用分子动力学方法,对含有预置微裂纹α-Ti模型施加不同方向拉伸载荷,通过观察模型内孔洞及位错的变化情况,揭示了孔洞生长的机制与初始缺陷对材料吸收能量在不同划分区域的规律。研究发现:当拉伸载荷沿着垂直于密排面的[0001]方向时,预置裂纹愈合,α-Ti会从hcp晶格转换为fcc晶格,从而使晶体中的位错种类更多、密度更大、能量吸收率更高;当拉伸载荷沿着[1230]方向拉伸时,位错种类主要为1/3[1210]类型,裂纹则生长为一定尺寸的孔洞,孔洞与滑移带对模型体系吸收能量区域有划分作用,转换的晶格主要为非晶结构,滑移带方向取决于材料晶格,位置取决于初始裂纹;α-Ti沿[0001]晶向拉伸后模型明显颈缩,裂纹缺陷空位被两侧团簇占据,α-Ti沿[0001]晶向拉伸比沿[1230]方向拉伸时拥有更好的塑性和延展性。

Using the molecular dynamics method,we applied tensile loads in different directions to a preset-microcracksα-Ti model.Through the observation of the changes in the pores and dislocations of theα-Ti model,we revealed the mechanism of the pore growth and the potential energy distribution.We found that under the tensile load along[0001],the perpendicular direction of the close-packed plane,the preset crack in the model closes up,the clusters on both sides occupy the gap of crack defect,showing an obvious necking phenomenon,and part of the hcp lattice transform into the fcc lattice to plane,which derive a variety of dislocations with higher density in the crystal.Therefore,it can bear more press.Under the tensile load along[1230],the dislocation types are mainly 1/3[1210]with less total length than in[0001].The crack grows into a circular cavity.The cavity and sliding band divides the absorption energy regions into four parts.The lattice transformations are mainly from hcp to amorphous structure.The direction of the slip band depends on the material lattice and the position depends on the initial crack.Load on[0001]makes the necking phenomenon of the model prominent,and the crack defect vacancies are occupied by the clusters on left and right sides.Therefore,when loaded on[0001]theα-Ti has better plasticity and ductility than loaded on[1230].