1988 年 28 巻 10 号 p. 802-808
In order to design superplastic titanium alloys having an improved strength-density ratio, it is necessary to control the compositional and microstructural parameters such as volume fraction and degree of solid-solution strengthening for the primary a phase and electron-atom ratio for the prior β phase in titanium alloys. For that purpose, a method for calculation of α-β phase equilibria in multi-component titanium alloys, based on the analyses of a and β phase compositions, was developed by using multicomponent 20 titanium alloys. The reliability of the method was confirmed to be satisfactory by excellent agreements between the observed value and the value calculated by the method for the volume fraction of a phase and the partition ratio of each element between a and β phases in not only 20 alloys which were used to construct the method but also other 8 alloys. Furthermore, thermodynamic calculation was performed on multi-component 20 titanium alloys. The good agreements between the calculated value and the observed value for the volume fraction of α phase and the partition ratio of each element between α and β phases demonstrate that an adequately selected set of parameters can describe the thermodynamics of the α and β phases in multi-component titanium alloys.
