【作者】 崔新林；

【导师】 李英骏；

【作者基本信息】 中国矿业大学（北京） ， 固体力学， 2009， 博士

【摘要】 利用分子动力学计算模拟方法对单晶铁在冲击波压缩下,由体心立方(BCC)结构到六角密排(HCP)结构的相变过程及微观机理进行了分析研究。势函数选用Voter-Chen等提出的EAM势,通过分析冲击波压缩下相变原子的位移历史,获得了冲击相变的微观机制,相变机制包含压缩和滑移两步,同时发现相变只是出现在某些特定的{011｝面上。通过在样品中预置一个纳米孔洞,研究了孔洞缺陷对冲击相变特征的影响。研究结果显示：孔洞缺陷的存在没有改变铁的冲击相变机制,但是孔洞缺陷明显降低了相变阈值应力,加速了相变成核速率,改变了相变的初始成核区域；孔洞反射的稀疏波对相变成核区域的影响随孔洞体积增大而增大,导致孔洞周围出现了大量的无序结构原子;孔洞对相变的影响也体现在粒子速度剖面上,压缩过程中孔洞周围出现大量的“热点”,导致了更低的粒子速度分布。更多还原

【Abstract】 The shock-induced phase transformation and micro-mechanism of single crystal iron from the body-centered cubic phase to hexagonal close-paced phase have been investigated by means of molecular dynamics (MD) simulation, Voter-Chen EAM potential has been used to study the shock-induced phase transformation of iron. By analyzing the moving history of atoms under shock wave compression, the results show that the phase transformation mechanism contains two steps: the compression and the shift courses, respectively. The slip planes have been observed only at some special{011} planes under shock loading. In addition, a nanovoid is settled in the center of the sample to show the effect of defect on the phase transformation, and the results show that the void doesn’t change the phase transformation mechanism, but reduces the threshold of pressure and accelerates the nucleation speed of the phase transformation. Also, the void changes the phase transformation nucleation sites, and yields a lot of atoms with amorphous structure around the void. The effect of void is further shown in the particle velocity profile by the production of a lot of "hot spot", which leads to the lower particle velocity in the defective iron.更多还原