金属玻璃形成液体的热力学特性

通过分析规则熔体的热力学模型，计算了典型金属玻璃的熔体混合焓ΔH^mix和混合熵ΔS^mix.结合临界冷却速率，归纳出典型金属玻璃形成液体的热力学特性,并提出基于原子尺寸、元素组成以及元素之间混合焓等参数的形成大块金属玻璃的成分判定方法.结果表明，当ΔH^mix<-15 kJ·mol^-1且ΔS^mix>0.6 J·K^-1mol^-1时，合金易于形成大块金属玻璃.金属玻璃的临界冷却速率R_c具有明显的尺寸效应，其值与熔体的ΔS^mix值呈指数关系，可以用R_c＝42.24×10⁴exp(-13.91ΔS^mix)+19.66粗略判断.运用该方法成功设计并制备出远离原有Zr基大块金属玻璃形成区域(55at%—65at%Zr)的Zr₄₀Al₁₀Ni₁₅Cu₃₅和四元Fe-B基Fe₅₃Co₅Nd₁₂B₃₀大块金属玻璃. 关键词： 混合焓 混合熵 大块金属玻璃 玻璃形成能力

Thermodynamic characteristics of metallic glass-forming liquids

On the basis of analyzing the thermodynamic model of regular melt, the mixing enthalpy ΔH^mix and the mixing entropy ΔS^mix of typical metallic glass melts were calculated. The distribution of ΔH^mix vs. ΔS^mix for typical metallic glasses was generalized, and a strategy for pinpointing metallic glass formers has been proposed by combining the critical cooling rate R_c based on the atomic intrinsic characteristics of the alloys including atom size, composition, and mixing enthalpy of binary systems among the components. On the condition of ΔS^mix greater than 0.6 J·K^-1mol^-1 and ΔH less than -15 kJ·mol^-1, the alloy tends to form a bulk metallic glass(BMG). It shows that R_c is intimately related with ΔS^mix, and can be expressed as R_c=42.24×10⁴ exp(-13.91 ΔS^mix)+19.66. Two new glass formers, Zr₄₀Al₁₀Ni₁₅Cu₃₅, located far from the glass forming area of the existing Zr-Al-Ni-Cu BMGs with a content of 55at%—65at% zirconium, and Fe₅₃Co₅Nd₁₂B₃₀ of quaternary Fe-B-based BMG, were successfully prepared with this approach.