CoCrFeMnNi高熵合金冲击波响应与层裂强度的分子动力学研究

高熵合金未来有望应用于航空航天和深海探测等领域, 并且不可避免地会受到极端冲击载荷作用, 甚至会发生层裂. 本文采用分子动力学(MD)方法, 研究了CoCrFeMnNi单晶高熵合金冲击时的冲击波响应、层裂强度以及微观结构演化的取向相关性和冲击速度相关性. 模拟结果表明, 在沿110]和111]方向进行冲击时产生了弹塑性双波分离现象, 且随着冲击速度的增加呈现出先增强后减弱的变化趋势, 但在沿100]方向冲击时未出现双波分离现象. 在冲击过程中, 大量无序结构产生且随冲击速度的增加而增加, 使得层裂强度随冲击速度的增加而减小. 此外, 层裂强度也具有取向相关性. 沿100]方向冲击时产生了大量体心立方(BCC)中间相, 抑制了层错以及无序结构的产生, 使得100]方向的层裂强度最高; 层裂初期微孔洞形核区域无序结构含量大小关系的转变, 使得111]方向的层裂强度在冲击速度较低时(U_p≤0.9 km/s)大于110]方向, 而在冲击速度较大时(U_p≥1.2 km/s)略小于111]方向. 研究成果有望为 CoCrFeMnNi高熵合金在极端冲击条件下的应用提供理论支撑和数据积累. 

SHOCK WAVE RESPONSE AND SPALL STRENGTH IN CoCrFeMnNi HIGH-ENTROPY ALLOY: A MOLECULAR DYNAMICS STUDY

High-entropy alloys are expected to be used in aerospace, deep-sea exploration and other fields in the future, and will inevitably be affected by extreme shock loading, even will occur spall fracture. In this work, the molecular dynamics (MD) method is used to study the orientation and shock velocity dependence of the shock wave response, spall strength and microstructure evolution of single-crystal CoCrFeMnNi high-entropy alloys. The simulation results show that the elastoplastic two-wave separation phenomenon occurs when the shocking along the 110] and 111] directions and shows a trend of first strengthening and then weakening with the increase of the shock velocity. However, there is no two-wave separation phenomenon when the shocking along the 100] direction. During the shocking process, a large number of disordered structures are generated and increase with the increase of the shock velocity, which makes the spall strength decreases with the increase of shock velocity. In addition, the spall strength also exhibits orientation dependence. A large number of body-centered cubic (BCC) intermediate phases are generated when the shocking along the 100] direction, which inhibits the generation of stacking faults and disordered structures, making the highest spall strength in the 100] direction; The transformation of the relationship of the content of disordered structure in the nucleation area of microvoids at the early stage of spallation, making the spall strength in the 111] direction is higher than that in the 110] direction when the shocking velocity is low (U_p≤0.9 km/s), and slightly lower than that in the 110] direction when the shocking velocity is large (U_p ≥1.2 km/s). The research results are expected to provide theoretical support and data accumulation for the application of CoCrFeMnNi high-entropy alloys under extreme shock conditions.