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对金属熔体结构的研究证实熔体中存在短程有序结构,而含金属间化合物的合金熔体中发现了原子-分子结合的团簇结构,即固态下的金属间化合物在熔体中并没有消失,而是以团簇结构(实际上就是液态的分子)存在,并与熔体中的自由原子存在化学平衡。从熔体结构出发,提出了适用于合金熔体的原子-分子热力学模型。然后以Ca-Mg合金熔体为例,介绍了该模型的构建和求解方法,并计算了1 010K下的Ca-Mg合金熔体中各物质的摩尔分数。最后,将计算得到的钙、镁摩尔分数与各自的实测活度值进行比较,发现两者吻合得较好。这从计算上证明了合金熔体中同时存在着金属原子和金属间化合物分子,两者处于动态化学平衡之中。且达到平衡时,金属原子的摩尔分数实际上就是各自的活度。因此,对于合金熔体而言,活度并不存在。
The study on the structure of metal melt confirmed the existence of short-range ordered structure in the melt, and the cluster structure of atom-molecule bond was found in the alloy melt containing intermetallic compound, that is, the intermetallic compound in solid state was in the melt Does not disappear, but exists as a cluster structure (actually a liquid molecule) and is chemically balanced with the free atoms in the melt. Based on the melt structure, an atomic-molecular thermodynamic model suitable for alloy melt is proposed. Then taking the Ca-Mg alloy melt as an example, the construction and solution method of the model is introduced, and the mole fraction of each substance in the Ca-Mg alloy melt at 1,010K is calculated. Finally, comparing calculated calcium and magnesium mole fractions with their respective measured activity values, we found that the two agree well. This proves that there are both metal atoms and intermetallic compounds in the melt, which are both in a dynamic chemical equilibrium. And to reach equilibrium, the molar fraction of metal atoms is actually the respective activity. Therefore, the activity does not exist for the alloy melt.