High-temperature Deformation Characteristics of Sintered Ti-6Al-4V Alloy Produced by Blended Elemental Method

The high temperature deformation characteristics of sintered Ti-6Al-4V alloy were investigated using specimens produced by the process of blending of extra-low-chlorine Ti and 60 mass% Al-40 mass% V master alloy powders, CIP and vacuum sintering. Hot compression tests were carried out using Formaster test machine at the temperatures ranging from 1123 to 1323K and at the strain rates from 1x10 exp -3 to 5.8x10 exp 1 s exp -1 . Cracks are formed more easily in the specimens with lower relative density and at the higher reduction ratio. At the temperatures in the single beta phase region, the crack formation becomes easier at the higher strain rates. On the other hand, higher strain rates rather suppress crack formation at the temperatures in the alpha + beta two phase region. The flow stress, deformation temperature and strain rate can be correlated with Zenner-Hollomon parameter, and the activation energy for deformation is higher than the previously reported value which was obtained using wrought material. Hot deformation converts the coarse microstructures in the as-sintered specimens to refined ones, which are believed to exhibit excellent mechanical properties.