Understanding of the thermomechanical processing that affects microstructures is important to develop new alloys, because the mechanical properties of Ti alloys depend on the microstructures. In our previous study, we found Sn deteriorated the oxidation resistance, while Nb improved the oxidation resistance. Then, we have focused on Ti-Al-Nb-Zr alloys which Nb was added instead of Sn. Zr was added for solid solution strengthening. In this study, the formation of microstructures by thermomechanical processing and the effect of microstructure on the mechanical properties were investigated using the Ti-13Al-2Nb-2Zr (at%) alloy. The samples heat-treated in the β+α phase followed by furnace cooling after processed in the β+α phase formed the equiaxed or the ellipsoid α phase surrounded by the β phase. On the other hand, the sample heat-treated in the β+α phase followed by furnace cooling after processed in the β phase formed the lamellar microstructure. The compression strengths of the equiaxed α structure processed at two temperatures in the β+α phase were almost the same. While creep life of the bi-modal structure was drastically changed by processing temperature.

The morphology of γ/γ' microstructures in single crystal superalloys is known to evolve during service conditions according to established materials science principles, potentially offering a novel approach for failure analysis. This study investigated the morphological changes in γ/γ' microstructures of CMSX-4, a single crystal Ni-base superalloy, under various loading conditions. The experimental parameters included tensile and compressive stress levels, loading temperature, loading rate, monotonic versus cyclic loading, and multi-axial stress states. Results demonstrated that the γ/γ' microstructures exhibited highly sensitive responses to these loading conditions. A newly developed quantitative image analysis method was used to characterize these morphological changes, and the findings were compiled into a two-dimensional map to facilitate failure analysis and other engineering applications.