材料期刊网

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1010 K 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。

Based on the research of the structure of molten metal,it has been proved that the short-range order struc-tures is existing in molten metal and atom-molecule clusters have been found in alloy melts containing intermetallic compounds,that is to say,the intermetallic compounds in solid do not disappear in alloy melts.Actually,clusters in alloy melts are exiting in molecules,which constitutes chemical equilibrium with free atoms in melts.On the basis of the structure of molten metal,a atom-molecule thermodynamic model which is suitable for the molten metal has been put forward.Then taking the Ca-Mg alloy melts for example,the modelling and solving method of the thermody-namic model has been introduced and the mole fraction of each component in Ca-Mg alloy melts has been calculated at 1 010 K.By comparison,the calculated mole fractions are consistent with the reported activities of Ca and Mg in Ca-Mg binary melts,which has proved both metal atoms and intermetallic compound molecules are simultaneously existing in alloy melts and are in the dynamic chemical balance.When they reach the chemical balance,the mole fraction of metal atoms actually equals their activity.Therefore,there is no activity for alloy melts.