ELEVATED-TEMPERATURE TENSILE BEHAVIOR OF TI-25AL-10NB-3V-1MO

The effects of microstructure and temperature on tensile and fracture behavior were explored for the titanium aluminide alloy Ti-25Al-10Nb-3V-1Mo (atomic percent), Three microstructures were selected for study in an attempt to determine the role of the individual microstructural constituents in this alpha(2) + B2 alloy. Tensile testing of both round and flat specimens in vacuum indicated a change in deformation behavior from 25 degrees C to 450 degrees C. Observations suggested that this change in deformation behavior occurred within the alpha(2) phase. Failure initiation at 450 degrees C and above was by a ductile process and was associated with the B2 phase. Above 600 degrees C and at high strains, plastic deformation occurred predominantly in the B2 phase. Strain localization was observed above 600 degrees C and found to be due to the lower work-hardening rate of the B2 phase. Strain localization at slip band intersections with prior beta grain boundaries resulted in rapid strain accumulation in the B2 phase. Alignment of secondary alpha(2) laths with the tensile axis at high deformation levels appeared to inhibit shear band localization between voids due to a lack of participation of the alpha(2) phase in deformation.