金属钛辐照级联过程缺陷演化的分子动力学模拟

Molecular Dynamics Simulation on Irradiation-induced Defect Evolution in Titanium

钛合金材料因其优异的耐腐蚀性能和机械性能被认为是反应堆的候选结构材料。本文围绕材料服役过程中的辐照损伤机制问题,采用分子动力学(MD)方法研究了金属钛(以α-Ti为例)的辐照级联过程,获得了不同温度(300、500、700和900 K)、不同能量(1、5、10和20 keV)的初级碰撞原子(PKA)沿不同晶格方向([0001]、[1010]和[1100])入射的碰撞过程,并从原子尺度分析了α-Ti在辐照级联过程下的缺陷演化行为及机制。结果表明,随着温度升高,α-Ti级联碰撞过程诱发的峰值点缺陷数明显增加,缺陷复合过程所需时间延长;随着PKA能量增加,整个缺陷演化过程的缺陷数均明显增加,稳定缺陷数也呈增加趋势;而PKA入射方向对级联过程中缺陷演化无明显影响。采用NRT(Norgett-Robinson-Torrens)模型计算获得α-Ti辐照缺陷随PKA能量的变化趋势与MD计算结果一致,级联碰撞后剩余的缺陷数约占NRT预测值的30%。本文从微观角度研究了金属钛的辐照损伤机理,相关计算结果为钛合金在未来核反应堆中的应用提供数据支持,为新型耐辐照材料研发提供理论依据。

Titanium base alloys can be used as potential candidate of structural materials in nuclear reactor due to their outstanding corrosion resistance and mechanical properties.By using molecular dynamics(MD)methods,this paper simulated the displacement cascade processes inα-Ti metal at various temperatures(T=300,500,700 and 900 K)with primary knock-on atom(PKA)(E_(PKA)=1,5,10 and 20 keV)incident in various directions([0001],[1010]and[1100]).The displacement cascades were designed as follows,the model was initially relaxed at each specified temperature for 10 ps with periodic boundary conditions applied.Then,a PKA was randomly selected and assigned specific kinetic energy to initiate the displacement cascade.At length,the data production,defect analysis and visualization were done to elucidate the irradiation cascade processes.The results show that the defect number increases with the increase of PKA energy or temperature,whereas the incident directions of PKA does not affect the defect number during the evolution a lot.With the increase of temperature,the number of peak defects inα-Ti increase significantly,and the time required for the defect recombination process extends.With the increase of PKA energy,the number of defect in the entire defect evolution process increases significantly,and the steady-state defect number also shows an increasing tendency.However,the PKA incident direction has slightly effect on the defect evolution during the cascade process.The Norgett-Robinson-Torrens(NRT)model was used to calculate the trendency of defect number as functional of PKA energy and it is consistent with the MD calculations.Considering the simulated temperature and PKA energy,and the number of remaining defects after cascade collision accounted for about 30%of NRT.The results in this paper help to understand the primary irradiation defect and atomic effect evolution mechanisms inα-Ti from the perspective of theoretical calculations.Moreover,discussing how to enhance the radiation resistance of metallic titanium and titanium alloys under the current theoretical research content has certain guiding significance for the design of future nuclear reactor shell materials.