单轴应变驱动铁bcc—hcp相转变的微观模拟

用分子动力学方法模拟了沿〈001〉晶向应变加载和卸载情况下单晶铁中体心立方(bcc)与六方密排(hcp)结构的相互转变,分析了相变的可逆性和微结构演化特征.微观应力的变化显示样品具有超弹性性质,而温度变化表明在相变和逆相变过程中均出现放热现象.相变起始于爆发式均匀形核,晶核由块状颗粒迅速生长为沿{011}晶面的片状分层结构; 而卸载逆相变则从形核开始就呈现片状形态,且相界面晶面指数与加载相变完全一致,表现出形态记忆效应.在两hcp晶核生长的交界面易形成面心立方(fcc)堆垛层错. fcc通过在hcp晶粒内

Atomistic simulation of the bcc-hcp transition in iron driven by uniaxial strain

The bcc—hcp structural transition in single crystal iron under 〈001〉 uniaxial strain has been investigated by molecular dynamics simulation. The reversibility and the morphological characteristics are discussed. The stress history indicates a super-elastic deformation in the sample, while the change of temperature shows the heat release during both hcp and bcc nucleation. A laminated structure of bcc and hcp along {011} planes is obtained, where the phase boundaries for the bcc to hcp and hcp to bcc transition are found along the same plane, implying the memory effect of morphology. Stacking faults (fcc) can be formed at the interface between hcp nuclei. For the bcc to hcp transition, we observed the mergence of the stacking faults in an hcp grain and the position adjustment between hcp grains. No migration of stacking fault is found during the hcp to bcc transition. In addition, the bcc—hcp transition structure is analyzed by the radial distribution function.