Abstract

The thermodynamic properties of bcc and fcc iron phases are calculated at the temperature of the polymorphic bcc–fcc phase transition using the method of calculating properties of a crystal developed before on the base of the Mie–Lenard-Jones pairwise potential. 23 properties of iron and their changes during the bcc–fcc transition have been calculated. The calculations show that the properties, such as: the Grüneisen parameter, the thermal expansion coefficient, and the specific heat are only slightly changed during the bcc–fcc transition. The modulus of elasticity, the specific entropy, the Poisson ratio, and the specific surface energy are changed as well as the molar volume, i.e., within the limit of 1%. The Debye temperature and its pressure derivative decrease during the bcc–fcc transition in the same manner as the distance between the centers of the nearest atoms, i.e., within 2–3%. The analysis of the available experimental data shows that even comparatively correctly measured parameters, such as the thermal expansion coefficient and the modulus of elasticity, are measured with an error higher than the jumps of these parameters during the bcc–fcc transition. It is shown that amorphization or the nanostructurization of a certain iron fraction during the bcc–fcc transition is indicated can contribute to the changes in the iron properties during this phase tr-ansition.

中文翻译：

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BCC-FCC相变过程中铁的性质变化

摘要

bcc和fcc铁相的热力学性质是在计算多态性bcc-fcc相变温度时，使用计算以前基于Mie-Lenard-Jones成对电势形成的晶体的性质的方法来计算的。计算了23种铁的性质及其在bcc-fcc转变过程中的变化。计算结果表明，在bcc-fcc过渡过程中，诸如Grüneisen参数，热膨胀系数和比热之类的属性仅略有变化。改变弹性模量，比熵，泊松比和比表面能以及摩尔体积，即在1％的范围内。在bcc-fcc转变期间，德拜温度及其压力导数以与最近原子中心之间的距离相同的方式降低，即在2-3％之内。对可用实验数据的分析表明，即使是相对正确测量的参数（例如热膨胀系数和弹性模量），其测量误差也高于在bcc-fcc过渡期间这些参数的跳跃。结果表明，表明在bcc-fcc转变过程中某些铁馏分的非晶化或纳米结构化可有助于此相变过程中铁性能的变化。诸如热膨胀系数和弹性模量的测量误差高于在bcc-fcc过渡期间这些参数的跳跃。结果表明，表明在bcc-fcc转变过程中某些铁馏分的非晶化或纳米结构化可有助于此相变过程中铁性能的变化。诸如热膨胀系数和弹性模量的测量误差高于在bcc-fcc过渡期间这些参数的跳跃。结果表明，表明在bcc-fcc转变过程中某些铁馏分的非晶化或纳米结构化可有助于此相变过程中铁性能的变化。