Compressive Properties and Deformation Mechanisms of Hot-Pressed Sintered Nb-23Ti-15Al Ultra-High Temperature Alloys

Nb-23Ti-15Al alloys were synthesized via hot-pressing sintering at different temperatures （1 350 ℃, 1440 ℃）, and their compressive deformation behaviors and deformation mechanisms of the alloys at both room temperature and high temperature （1 100 ℃） were investigated. The results show that the room-temperature compressive strengths of the alloys sintered at 1 350 ℃ and 1 440 ℃ reached 1 740 MPa and 2 200 MPa, respectively.. However, both alloys fractured without yielding during room temperature compression, indicating the high brittleness at room temperature. Under high temperature compression, the compressive strengths of the alloys prepared at the two sintering temperatures were similar, and both exhibited excellent plasticity, with strains exceeding 50% without fracture, along with noticeable strain softening. The strain softening was more pronounced in the alloy sintered at 1 440 ℃. During high temperature compression, deformation in both alloys was concentrated in the β phase. In the alloy sintered at 1 350 ℃, dislocation tangles and kinks were observed in the β phase, with no obvious slip bands, indicating relatively low deformation localization. Additionally, only a few parallel dislocations were present in the δ phase, and curved dislocations or dislocation arrays were identified within some Ti（O, C） phases. In contrast, the alloy sintered at 1 440 ℃ showed significant deformation localization in the β phase, where distinct slip bands were formed, and a high density of dislocations was accumulated within these bands.