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arXiv 2103.12384cond-mat.mtrl-sci
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不互溶二元系Fcc -> bcc相变动力学:相变孪晶机制的原子证据

Fcc -> bcc phase transition kinetics in an immiscible binary system: atomistic evidence of the twinning mechanism of transformation

G. Demange, M. Lavrskyi, K. Chen, X. Chen, Z. D. Wang, R. Patte, H. Zapolsky

摘要:

基于准粒子(QA)方法进行了广泛的原子模拟,以确定在一个二元系统中的位移fcc/bcc相变的重要方面。我们表明,QA是能够预测的fcc/bcc相变的主要结构特征,包括在fcc矩阵的bcc核的生长,并最终形成的内部孪生结构组成的两个变种与Kurdjumov-Sachs取向关系。在原子水平上,我们确定了孪晶界面和面心立方/体心立方界面的缺陷结构,并确定了其传播的主要机制。结果表明,孪晶界是通过fcc中螺旋位错沿α方向的扩展而扩展<-1-11>的,而fcc中螺旋位错沿共格台阶边缘的扩展是fcc/bcc转变的关键矢量。将模拟结果与我们在Cu-Fe-Co系统中观察到的富Fe bcc孪晶颗粒镶嵌在fcc富Cu基体中的TEM和HRTEM结果进行了比较。

英文摘要:

Extensive atomistic simulations based on the quasiparticle (QA) approach are performed to determine the momentous aspects of the displacive fcc/bcc phase transformation in a binary system. We demonstrate that the QA is able to predict the major structural characteristics of fcc/bcc phase transformations, including the growth of a bcc nuclei in a fcc matrix, and eventually the formation of an internally twinned structure consisting in two variants with Kurdjumov-Sachs orientation relationship. At atomic level, we determine the defect structure of twinning boundaries and fcc/bcc interfaces, and identify the main mechanism for their propagation. In details, it is shown that twin boundaries are propagated by the propagation of screw dislocations in fcc along the <-1-11>_α direction, while the propagation of fcc screw dislocations along coherent terrace edges is the pivotal vector of the fcc/bcc transformation. The simulation results are compared with our TEM and HRTEM observations of Fe-rich bcc twinned particle embedded in the fcc Cu-rich matrix in the Cu-Fe-Co system.

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