Pt-Pd体系的热力学评估

Thermodynamic assessment of Pt-Pd system

采用CALPHAD(计算相图)方法首先对Pt-Pd体系各相吉布斯自由能分别建模,通过拟合热力学实验数据,获得两套热力学参数。该参数可用于相组分、相图相变、希尔凝固路径及微观组织结构演化模拟等研究领域,利于高性能合金成分设计。针对Pt-Pd体系中面心立方相(Fcc)混溶间隙是否存在的争论,基于最新的实验数据,使用Thermo-calc软件中的Parrot模块分别对两种情况进行热力学优化。通过优化获得的两套自洽的热力学参数,计算并比较了两种情况下的吉布斯自由能,证实了实验中发现的混溶间隙处于一种亚稳态。Fcc亚稳相图提供了混溶间隙范围内的相组成信息,平衡相图预测的热力学性质则与实验数据高度一致。

In this work,the CALPHAD(Computational Phase Diagram)method was used to model the Gibbs free energy of each phase of the Pt-Pd system,and two sets of thermodynamic parameters were obtained by fitting the thermodynamic experimental data.These parameters can be applied to the simulation of phase composition,phase transformation,Scheil solidification path,and microstructure evolution,etc.They are also conducive to the design of high-performance alloy composition.In response to the debate about the existence of the Face Center Cubic(Fcc)miscibility gaps in the Pt-Pd system,the Parrot module in the Thermo-calc software was utilized to thermodynamically optimize the two cases separately,based on the latest experimental data.The Gibbs free energy was calculated by optimizing the two sets of selfconsistent thermodynamic parameters and the results were then compared.It has been confirmed that the miscible gap is in a metastable state.The FCC metastable phase diagram provides phase composition information in the miscible gap range,and the thermodynamic properties predicted by the equilibrium phase diagram are highly consistent with the experimental data.