Effects of Zr addition on the high-temperature compressive and creep properties of the TiAl alloy

In this study, we systematically investigate the effects of Zr addition on the microstructural evolution, high-temperature compressive properties, and creep behavior of the TiAl alloy. The results reveal that the solidification microstructure of the Ti-45Al alloy transitions from a fully lamellar microstructure to a nearly lamellar microstructure with increasing Zr content, accompanied by a concomitant reduction in grain size and lamellar spacing. Regarding high-temperature compressive properties, the compressive strength shows a progressive enhancement, while the fracture strain initially increases before subsequently decreasing. The superior compressive strength of the Ti-45Al-4Zr alloy is primarily attributed to lamellar refinement and solid solution strengthening, whereas the enhanced plasticity of the Ti-45Al-2Zr alloy arises from effective coordinated deformation between the blocky γ phase and lamellar structures. In terms of creep properties, both creep strain and steady creep rate initially increase and then decrease with increasing Zr content. Notably, the Ti-45Al-4Zr alloy exhibits significantly improved creep resistance compared to the Ti-45Al-2Zr alloy, approaching the performance level of the Ti-45Al alloy. The higher concentration of Zr contributes to a more pronounced solid solution strengthening effect and facilitates the formation of nanoscale twins, which effectively inhibit dislocation climb. The improved creep resistance of the blocky γ phase in the Ti-45Al-4Zr alloy mitigates the detrimental effects associated with the increased content of the blocky γ phase. Additionally, the refined lamellae and superior microstructural stability further contribute to the improvement of creep performance.