Abstract: The hot deformation behaviors of alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si in the temperature range from 780 ℃ to 1 080 ℃, strain rate range from 0.001 s^-1 to 70.000 s^-1 are studied by means of isothermal constant strain rate compressing testing on a THERMECMASTOR-Z hot simulator, and the characteristics of flow stress curves and the effect of the deformation parameters on adiabatic shear and flow localization are obtained. The power dissipation map is developed on the basis of the flow stress data as a function of temperature, strain rate，and strain. The results show that the flow stress is sensitive to deformation temperature and strain rate. The flow softening characteristic appears at the range of low temperature and high strain rate while the steady state flow characteristic appears at the range of high temperature and low strain rate. As revealed by the power dissipation map and microstructure, alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si exhibits a wide region of flow instability manifested by adiabatic shear bands and flow localization at the strain rate above 0.100 s^-1 in the α+β phase field in which the power dissipation efficiency is less than 0.16.

Key words: titanium alloys, adiabatic shear band, flow localization, power dissipation map, microstructure