CAJ | 학술논문

采用分子动力学方法对 Mg7Zn3合金快速凝固过程进行计算机模拟，研究玻璃转变过程局域结构与动力学之间的关联。结果表明：以Mg原子为中心的FK多面体和以Zn原子为中心的二十面体局域结构，对Mg7Zn3金属玻璃的形成起关键性作用。Mg(Zn)原子的扩散系数在熔点附近开始偏离Arrhenius关系，而满足幂指数规律。根据均方位移、非相干中间散射函数和非Gauss函数等时间相关函数，发现：随着温度的降低，β驰豫越来越显著，α弛豫时间以VFT指数规律迅速增加；而且半径较小的Zn原子比Mg原子呈现较快的弛豫动力学行为。另外，部分短程有序局域原子结构具有较慢的动力学行为，对β驰豫中笼子效应起主导作用；并随着其数目的大量出现，体系扩散系数开始偏离Arrhenius关系，玻璃形成过程微观结构转变温度TgStr与动力学转变温度Tc非常接近。
채용분자동역학방법대 Mg7Zn3합금쾌속응고과정진행계산궤모의，연구파리전변과정국역결구여동역학지간적관련。결과표명：이Mg원자위중심적FK다면체화이Zn원자위중심적이십면체국역결구，대Mg7Zn3금속파리적형성기관건성작용。Mg(Zn)원자적확산계수재용점부근개시편리Arrhenius관계，이만족멱지수규률。근거균방위이、비상간중간산사함수화비Gauss함수등시간상관함수，발현：수착온도적강저，β치예월래월현저，α이예시간이VFT지수규률신속증가；이차반경교소적Zn원자비Mg원자정현교쾌적이예동역학행위。령외，부분단정유서국역원자결구구유교만적동역학행위，대β치예중롱자효응기주도작용；병수착기수목적대량출현，체계확산계수개시편리Arrhenius관계，파리형성과정미관결구전변온도TgStr여동역학전변온도Tc비상접근。
The rapid solidification process of Mg7Zn3 alloy was simulated by the molecular dynamics method. The relationship between the local structure and the dynamics during the liquid-glass transition was deeply investigated. It was found that the Mg-centered FK polyhedron and the Zn-centered icosahedron play a critical role in the formation of Mg7Zn3 metallic glass. The self-diffusion coefficients of Mg and Zn atoms deviate from the Arrhenius law near the melting temperature and then satisfy the power law. According to the time correlation functions of mean-square displacement, incoherent intermediate scattering function and non-Gaussian parameter, it was found that the β-relaxation in Mg7Zn3 supercooled liquid becomes more and more evident with decreasing temperature, and the α-relaxation time rapidly increases in the VFT law. Moreover, the smaller Zn atom has a faster relaxation behavior than the Mg atom. Some local atomic structures with short-range order have lower mobility, and they play a critical role in the appearance of cage effect in theβ-relaxation regime. The dynamics deviates from the Arrhenius law just at the temperature as the number of local atomic structures begins to rapidly increase. The dynamic glass transition temperature (Tc) is close to the glass transition point in structure (TgStr).