Comparison of high-temperature deformation behaviors for Ti-Al-Nb-V alloy with different initial microstructures at the strain of 0.7

The Ti-Al-Nb-V alloy with the Widmanstatten B2+alpha(2) structure was prepared by induction skull melting, and it became single-B2-phase alloy with the equiaxed structure by further solution treatment and quenching. The compression properties and the deformation behaviors of the Ti-Al-Nb-V alloy with the two types of microstructures were investigated in the temperature range of 500-900 degrees C. When the alloy was loaded at 500-800 degrees C, the yield strength of the specimen with the equiaxed structure was higher than that of the one with the Widmanstatten structure, whereas the opposite trend was exhibited at 900 degrees C. For the specimen with the Widmanstatten structure, the flow softening occurred at 600-900 degrees C upon compression, and the initiating strain of the flow softening stage decreased with the increasing deformation temperature. For the specimen with the equiaxed structure, the flow softening occurred at 500-900 degrees C. By comparing the undeformed and deformed microstructures of the specimens at the strain of 0.7, it was concluded the deformation mechanism of the specimen with the Widmanstatten structure was dislocation glide below 600 degrees C, and above this temperature, dynamic recrystallization in the B2 phase became dominant. For the specimen with the equiaxed structure, the deformation mechanism was the dislocation glide that formed the slip bands at 500 degrees C, while recrystallization occurred in the slip bands at 600-900 degrees C, leading to the flow softening. When the deformation temperatures were 800 degrees C and 900 degrees C, the deformation mechanism also referred to the phase transformation of B2 ->alpha(2). According to the detailed microstructure observations, the deformation mechanisms were schematically illustrated for the Ti-Al-Nb-V alloy with different initial structures.