Effect of hot-rolling temperature on microstructure and dynamic mechanical properties of Ti–6Al–4V

Abstract:

The equiaxed Ti-6Al-4V alloys were rolled with an overall reduction ratio of 0.78 at 840℃, 870℃, 900℃ and 930℃, respectively. The microstructure, texture and anisotropy of dynamic mechanical properties of the rolled alloy were investigated. Results have shown that, recrystallization and phase transformation did not occur until the rolling was performed at a temperature higher than 900℃, and then the microstructure of the rolled alloy turned into bimodal, while the amount of lamellar α_s+β structure and recrystallized α grains showed an increasing tendency with the increased rolling temperature. Moreover, it was interesting to find that although the texture was varying with the rolling temperature, the <0001> direction of α phase kept parallel to the normal direction (ND) during the hot-rolling process at various temperatures. Based on the analyses of dynamic mechanical properties, Ti-6Al-4V alloy was observed to exhibit anisotropy of dynamic mechanical properties after hot-rolling at different temperature. However, resulting from the rolling-temperature-depended texture and distribution of dislocation, the anisotropic tendency of dynamic mechanical properties varied with the rolling temperature. Moreover, with the increased rolling temperature, the dynamic flow stress loaded along ND decreased, while the adiabatic shearing failure strain slightly increased. The dynamic flow stress loaded along RD remained constant, while the adiabatic shearing failure strain exhibited an obviously decreasing tendency with the increased rolling temperature. The dynamic mechanical properties loaded along Transverse Direction (TD) remained constant when the rolling temperature was in the range of 840℃ to 900℃, while the dynamic flow stress loaded along TD increased evidently when the rolling temperature reaches 930℃, but the adiabatic shearing failure strain decreased greatly.