含钡二元合金熔体热力学性质的计算

Calculation of Thermodynamic Properties in Binary Barium-Bearing Alloy Melts

根据Miedema二元合金生成热模型,结合相关热力学数据,对Si-Ca二元合金熔体在1623K时的组元活度进行了计算,计算结果与实测结果吻合较好。并进一步对Ba-Si、Ba-Al和Ba-Ca3种二元含钡合金熔体的生成热ΔH及1873K时的过剩熵SE、过剩自由能GE以及不同温度下各组元的活度等热力学性质进行了计算。结果表明:3种合金的ΔH、SE和GE均为负值,且SE绝对值的最大值为4·424J/mol,可以近似认为3种合金熔体的SE为零;Ba-Si和Ba-Al合金熔体的活度相对于理想溶液存在较大负偏差,而Ba-Ca合金熔体的活度与理想溶液偏差较小。

According to the Miedema formation heat model and retated thermodynamic data, the activity of Si-Ca binary alloy melt at 1 623 K was calculated. The calculated results are in good agreement with the experimental data. Excess entropy and excess free energy at 1 873 K and each component activity at the different temperature of Ba-Si, Ba-Al and Ba-Ca binary barium-bearing alloy melts were calculated. The results show that the values of formation heat, excess entropy and excess free energy of the melts all negative. The maximum value of Absolute value of excess entropy is 4.423 68 J/mol. So the excess entropy of the alloy melts approximately approaches zero. Activity curves of Ba-Si and Ba-Al alloy melts show a great negative deviation from the idea solution. However, activity curve of Ba-Ca alloy melt shows a small negative deviation from the idea solution which indicates the intersolubility of Ba-Ca alloy melt is perfect.