Deformation Behavior of Porous Ti-6Al-4V Alloy Samples Fabricated by Hot Isostatic Pressing

Abstract

In the present paper, hot uniaxial compression at elevated temperatures on the samples which had been hot isostatically pressed to 70%-100% relative densities was carried out to investigate the deformation behaviours of porous Ti-6Al-4V alloy. The results show that the flow stress and densification of Ti-6Al-4V alloy have a greater sensitivity on the deformation temperature and strain rate. The flow stress will increase as strain rate increases at the same temperature and the increasing of deformation temperature can lead to a decline in the flow stress at a specific rate. As the deformation temperature rises or the strain rate decreases, the relative density of compressed samples are higher. Moreover, the initial density affects the thermal deformation of powder compact to a certain extent. At the same strain, the greater the initial relative density of Ti-6Al-4V alloy is, the greater the flow stress will be. The flow stress sensitivity to relative density is much less than that to the temperature and strain rate. In addition, the higher the deformation temperature is, the more sufficient the process of alloy spheroidization will be. As the deformation rate decrease, the lamellar organization in the titanium alloy will convert into the equiaxed grains. The lower the deformation rate is, the more obvious the phenomenon of alloy globalization will be. There is not significant transition of the widmanstatten structure in the sample compressed for 2mm. When the sample was compressed for 5.6mm, a few equiaxed grains occurred. When the sample was compressed for 7mm, a large number of equiaxed grain occurred.