一维应变加载下单晶铁结构转变的微观研究

采用嵌入原子势和分子动力学方法，模拟了单晶铁在一维应变条件下由体心立方（bcc）转变为六角密排（hcp）结构的微观过程. 当应变加载至相变临界值时，hcp相开始均匀形核并沿{011}晶面长大为薄片状体系.弹性常数C₃₁和C₃₂在相变前被逐渐硬化，C₃₃则在相变前出现软化行为；当体系完全相变后，上述各弹性常数显示开始随体积压缩而迅速硬化，温度效应对晶格具有软化作用，可削弱C₃₃的硬化和软化过程；样品在压缩过程可出现孪晶结构，孪晶结构使晶格发生剪切变形.混合相中，hcp相势能比bcc相高，最大剪应力方向与bcc相反向；系统的偏应力与hcp相质量分数近似呈线性关系. 关键词： 结构转变 分子动力学 一维应变

Microscopic studies of structural transition in iron under one-dimensional strain

Molecular dynamics simulation employing an embedded-atom-method potential is performed to investigate the body-centered cubic（bcc）-hexagonal close-packed（hcp） structural transition in single crystal iron induced by isothermal compression along ［001］ divection. Above the critical strain of transition, homogeneous nucleation of hcp phase appears and grows into flakes along the （011） face. The elastic constants C₃₁ and C₃₂ harden during the compression in bcc phase, while C₃₃ undergoes a softening prior to the transition；all the elastic constants increase rapidly with compression after the system entering the hcp phase. Increasing temperature can weaken the hardening and softening process of C₃₃, but affect the stress threshold of transition only weakly. Hcp twins are formed at 300 K, leading to the shear of crystal latlice. For the mixed phase, the potential of hcp phase is greater than that of bcc phase, hcp phase shows an over-relaxation of the stress, and the longitudinal partial stress keeps linearly decreasing with hcp mass fraction throughout the transition.