ABSTRACT

The thermophysical properties of refractory MoNbReTaW high-entropy alloy in both supercooled liquid and high-temperature solid states were explored by an electrostatic levitation technique. The maximum supercooling attains 504 K, and the hypercooling limit is derived as 571 K. The liquid density at liquidus temperature is measured to be 13.3 g cm⁻³, which increases linearly with decreasing temperature at a slope of 6.83 × 10⁻⁴ g cm⁻³ K⁻¹. The liquid alloy exhibits 5.3% relative volume shrinkage during crystallization. The thermal expansion coefficient of liquid and solid alloy at liquidus temperature are determined as 5.0 × 10⁻⁵ K⁻¹ and 3.6 ×10⁻⁵ K⁻¹, respectively. The liquid specific heat at liquidus temperature is found to be 38.2 J mol⁻¹ K⁻¹, and basically displays a linear decreasing tendency with temperature. According to the calculated enthalpy of fusion 24.7 kJ mol⁻¹ and measured specific heats, the temperature-dependent entropy and Gibbs free energy difference between supercooled liquid and crystalline solid are obtained.

摘要

通过静电悬浮技术研究了难熔 MoNbReTaW 高熵合金在过冷液态和高温固态下的热物理性能。最大过冷度达到 504 K，过冷极限为 571 K。测得液相线温度下的液体密度为 13.3 g cm ^-3，随温度降低线性增加，斜率为 6.83 × 10 ^-4 g cm ^-3 K ^-1。液态合金在结晶过程中表现出 5.3% 的相对体积收缩率。液相线温度下液态和固态合金的热膨胀系数确定为5.0 × 10 ^-5 K ^-1和3.6 ×10 ^-5 K^-1，分别。发现液相线温度下的液体比热为38.2 J mol ^-1 K ^-1，并且基本上随温度呈线性下降趋势。根据计算的熔化焓24.7 kJ mol ^-1和测量的比热，得到过冷液体和结晶固体之间的温度相关熵和吉布斯自由能差。