Temperature-Dependent Effect of Deformation on Microstructure and Properties of TC4 Titanium Alloy

The effect of deformation temperature on the evolution of microstructure and properties of TC4 alloy was studied by a constant-strain rate tensile test at high temperature. The results show that both the peak stress and its required strain decrease with increasing temperature in the alpha+beta dual -phase field. The deformed microstructure exhibits a strong temperature-dependent evolution. Deformation leads to an accelerated recrystallization and refinement of primary a phase at a lower temperature of alpha+beta phase field (below 900 degrees C), whereas it results in a significant spheroidization of secondary a phase at a higher temperature (above 900 degrees C). Additionally, deformation also affects the nucleation and growth process of beta ->alpha transformation, resulting in a larger amount of secondary a phase. With the increasing deformation temperature, the volume fraction of a phase firstly decreases and then increases, and thus hardness has a good consistence. However, the corrosion resistance displays a reverse evolution with the amount of a phase. TC4 alloy exhibits the lowest volume fraction of a phase of 57% at the deformation temperature of 900 degrees C and the best corrosion resistance in a NaCl solution, while it shows a slightly lowered hardness.