运用分子动力学方法研究了hcp-Ti中的级联碰撞. 建立晶体结构模型, 选取不同的初级碰撞原子方向和能量, 分别研究了级联碰撞中所产生的点缺陷的演化情况, 给出初始物理图景. 对级联碰撞中的两大特征分布“离位峰”及“热峰”进行分析, 定量讨论了损伤区瞬态温度分布, 局部“熔化区域”的变化, 辐照诱发峰值缺陷数和稳定缺陷数等, 为分析材料辐照损伤行为提供了数据. 本工作中运用的计算方法可作为研究材料辐照诱发缺陷形成微观机制的一个有效手段.

The radiation-induced defects formed in nuclear structure materials in the initial stage of displacement cascade and the subsequent changes in their microstructures and mechanical properties are the primary causes of their failure. Unfortunately the formation and aggregation of point defects are hard to be found only by probed experiments. In this work, the displacement cascade occurring in hcp-Ti system has been investigated by using molecular dynamics. After building the atomic model, by setting different PKA (primary knock-on atom) directions and PKA energies respectively, the evolution of simulated radiation-induced point defects in displacement cascade was studied and its two major characteristics, displacement and thermal spikes, have been given. The transient temperature distribution, local “melting region” variation in the damage zone caused by radiation as well as the peak and surviving numbers of Frenkel pairs were quantitatively estimated. For hcp-Ti, in the PKA energy region of 0.5-9.0 keV, the effect of PKA velocity direction on survival defect number is very small. Both the defect number at stable state and its maximum value have approximately linear relationship with the PKA energy.In the radiation evolution stage, the defects about 95 percent have recovered, the defect and temperature distribution caused by displacement cascade are asymmetric. The simulation method used in this paper would provide an effective way for the study on the evolution and micromechanism of radiation-induced point defects in displacement cascade.