温度对六方系金属层错能影响的热力学模型

Thermodynamic Model for the Influence of Temperature on the Stacking Fault Energy in hcp Metals

摘要:

利用密排六方金属发生层错时在层错区域由密排六方 (Hexagonal Close-packed, hcp) 的AB排列转变为面心立方 (Face-centered Cubic, fcc) 的ABC排列的特点，通过计算hcp/fcc相变所需要的能量来计算hcp金属层错能。同时，在模型中引入了空位缺陷和温度等因素。利用此模型计算Mg，Zn，Ti等3种hcp纯金属的层错能，推导出层错能随温度变化的理论计算式，计算出变化值。计算结果表明：该热力学模型适用于hcp金属层错能的计算。Mg，Zn，Ti等hcp结构金属的层错能随着温度的升高逐渐降低，化学自由能变对层错能的影响占主导地位。空位有降低层错能的作用，随着温度的升高空位密度增大，层错能降低的幅度增大。

Abstract:

Based on the transition feature in procedure of producing stacking fault in hexagonal close-packed (hcp) metals that the atoms arrangement changes from AB (hcp) to ABC (fcc), the stacking fault energy (SFE) of hcp metals has been calculated from the energy of phase transition. In addition, the factors of vacancy defect and temperature have also been taken into account. Based on the thermodynamic model of stacking fault energy, the SFE of pure hcp metals Mg, Zn and Ti has been calculated. The equation of the influence of temperature on the SFE has also been established and finally the values of the equation have been calculated. The result shows that the thermodynamic model is fit perfectly for the pure hcp metals and the calculated results agree with the results calculated by first principle. The SFE of hcp metals is decreased gradually with the increasing temperature. The chemical free energy is also the key influence factor on SFE. In addition, vacancy can reduce the stacking fault energy of pure metals. The density of vacancy is increased with the increasing temperature and the devotion to the change of SFE is also increased.