共晶高熵合金形成的热力学基础研究

Basic Thermodynamic Research of Eutectic High Entropy Alloy Formation

摘要:

本文通过收集并总结已报道的18种共晶高熵合金的整体成分和各相成分等信息分别计算了反映其性质的一些参数,包括混合焓、混合熵、吉布斯自由能、原子尺寸实配度、电负性差和价电子数,并从热力学角度分析了这些参数对合金结构的影响规律。发现共晶高熵合金整体成分计算出的混合熵等值基本均满足传统高熵合金形成单相固溶体的结构判据要求(即△Smix >11 J/(mol·K)、-15 kJ/mol < △Hmix < 5 kJ/mol、δ < 6.6%等),但是由于其共晶相的平均自由能低于其整体形成单相时的总自由能,这使得共晶高熵合金在凝固过程中发生共晶反应,形成多相结构。

Abstract:

In this paper, by collecting and summarizing the reported overall composition and phase composition of 18 eutectic high-entropy alloys (EHEAs), some parameters reflecting their properties were calculated, including mixing enthalpy, mixing entropy, Gibbs free energy, atomic size mismatch, the electronegativity difference and the valence electron concentration , and the influence of these parameters on the structure of the alloy were analyzed from a thermodynamic point of view. It is found that the calculated mixed entropy equivalent of the overall composition of the eutectic high-entropy alloy basically meets the structural criterion requirements of the traditional high-entropy alloy to form a single-phase solid solution. (Such as △Smix >11 J/(mol·K)、-15 kJ/mol < △Hmix < 5 kJ/mol、δ < 6.6%) But because the average free energy of the eutectic phase is lower than the total free energy when the whole forms a single phase, this makes the eutectic high-entropy alloy in the solidification process A eutectic reaction occurs, forming a multi-phase structure.