Tang Ying, Zhang Lijun
School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China.
Materials (Basel). 2018 Sep 7;11(9):1648. doi: 10.3390/ma11091648.
As temperature increases, the thermal vacancy concentration in pure metals dramatically increases and causes some strongly non-linear thermodynamic behaviors in pure metals when close to their melting points. In this paper, we chose body-centered cubic (bcc) W as the target and presented a thermodynamic model to account for its Gibbs energy of pure bcc W from 0 K to melting point by including the contribution of thermal vacancy. A new formula for interaction part was proposed for describing the quadratic temperature behavior of vacancy formation energy. Based on the experimental/first-principles computed thermodynamic properties, all the parameters in the Gibbs energy function were assessed by following the proposed two-step optimization strategy. The thermodynamic behaviors, i.e., the strong nonlinear increase for temperature dependence of heat capacities at high temperatures and a nonlinear Arrhenius plot of vacancy concentration, in bcc W can be well reproduced by the obtained Gibbs energy. The successful description of thermal vacancy on such strongly non-linear thermodynamic behaviors in bcc W indicates that the presently proposed thermodynamic model and optimization strategy should be universal ones and are applicable to all other metals.
随着温度升高，纯金属中的热空位浓度急剧增加，并在接近熔点时导致纯金属出现一些强烈的非线性热力学行为。在本文中，我们选择体心立方（bcc）钨作为研究对象，并提出了一个热力学模型，通过考虑热空位的贡献来计算纯bcc钨从0 K到熔点的吉布斯自由能。提出了一个新的相互作用部分公式来描述空位形成能的二次温度行为。基于实验/第一性原理计算的热力学性质，按照提出的两步优化策略对吉布斯自由能函数中的所有参数进行了评估。所得到的吉布斯自由能能够很好地再现bcc钨中的热力学行为，即高温下热容量对温度的强烈非线性增加以及空位浓度的非线性阿累尼乌斯图。对bcc钨中这种强烈非线性热力学行为的热空位的成功描述表明，目前提出的热力学模型和优化策略应该是通用的，适用于所有其他金属。
