Balagurov Anatoly M, Samoylova Nataliya Yu, Bobrikov Ivan A, Sumnikov Sergey V, Golovin Igor S
Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980, Russian Federation.
National University of Science and Technology MISIS, Leninskiy prospekt 2, Moscow 119049, Russian Federation.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2019 Dec 1;75(Pt 6):1024-1033. doi: 10.1107/S2052520619013106. Epub 2019 Nov 9.
Structural features and kinetics of the transition between ordered metastable b.c.c.-derived D0 and equilibrium f.c.c.-derived L1 phases of Fe-xGa alloys (x = 27.2% and 28.0%) have been analyzed by in situ real-time neutron diffraction during isothermal annealing in the temperature range 405-470°C. It has been revealed that the transition proceeds with alternation of the first- and second-order phase transformations according to a D0 → A2 → A1 → L1 scheme, where A2 and A1 are disordered b.c.c. and f.c.c. structures. Deformations of the crystal lattice that arise due to these transitions are determined. The kinetics of the L1 phase nucleation and growth were analyzed in the frame of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model; however, only the early stage of the D0 → L1 transition is well described by the JMAK equation. The value of the Avrami exponent corresponds to the constant growth rate of the new L1 phase and decreasing nucleation rate in the Fe-27.2Ga alloy and indicates the presence of pre-existing nucleation centres of the L1 phase in the Fe-28.0Ga alloy.
通过在405 - 470°C温度范围内等温退火过程中的原位实时中子衍射，分析了Fe - xGa合金（x = 27.2%和28.0%）从有序亚稳体心立方衍生的D0相到平衡面心立方衍生的L1相转变的结构特征和动力学。结果表明，该转变按照D0→A2→A1→L1的模式进行，其中A2和A1分别为无序体心立方和面心立方结构，且一级和二级相变交替发生。确定了由这些转变引起的晶格变形。在约翰逊 - 梅尔 - 阿夫拉米 - 科尔莫戈罗夫（JMAK）模型框架内分析了L1相的形核和生长动力学；然而，JMAK方程仅能很好地描述D0→L1转变的早期阶段。在Fe - 27.2Ga合金中，阿夫拉米指数的值对应于新L1相的恒定生长速率和成核速率的降低，这表明在Fe - 28.0Ga合金中存在L1相的预先存在的形核中心。
