A physically-based model for elevated temperature strength prediction of (TiBw + (Ti, Zr)₅Si₃)/Ti-6.5Al-2Zr-1Mo-1V composite

In this paper, effects of heat treatment temperature and soaking time on the microstructure and elevated temperature mechanical properties of the (TiBw+(Ti, Zr)₅Si₃)/Ti-6.5Al-2Zr-1Mo-1V composite were studied. A physically-based model capable of predicting microstructure and yield strength was established. Results show that acicular martensite forms in the transformed β microstructure, the size of (Ti, Zr)₅Si₃ increases obviously, while the morphology of TiBw remain unchanged. With the increase of heat treatment temperature, the fraction of primary α phase and (Ti, Zr)₅Si₃ decreases, while the fraction of β_T increases. The yield strength and ultimate tensile strength of the composite are improved by 34% and 46% after heat treatment at 975 °C. The yield strength can be accurately predicted by the model. The mean relative error (MRE) of yield strength calculated by the model was 1.20% under the condition of heat treatment at 900 °C and 1050 °C. Using the model, martensitic strengthening accounts for the largest proportion in yield strength. The variation tendency of yield strength with temperature is predominantly decided by the variation tendency of martensitic strengthening. And the heat treatment temperature affects the yield strength through the factors including the fraction of β_T and the lamellae thickness of martensite.