Microstructural control of duplex Ti–46.5Al–2Cr–1.5Nb–1V alloys

The microstructural control of duplex Ti–46.5Al–2Cr–1.5Nb–1V (at%) is carried out in two steps: pretreatment and subsequent treatment. The pretreatment of the alloy includes fast cooling from α single-phase field and subsequent annealing at α+γ two phases field. The results show that the sample, which is oil quenched from 1320°C and then annealed at 1250°C has the most uniform and finest microstructure, and is suitable for subsequent microstructural control. In subsequent treatment, special heat-treatment processes are employed to obtain the duplex microstructure TiAl alloys with either different grain size at a constant lamellar grain fraction or different lamellar grain fraction at a constant grain size. The investigation of the microstructure transformation in the heat-treatment processes indicates that the grain size is strongly affected by the aging time in pretreatment process. The aging temperature plays a key role in controlling the lamellar grain fraction in subsequent treatment.