Effect of microstructural morphology on the mechanical properties of titanium alloys

Different morphologies of alpha+beta microstructures were obtained in a commercial Ti-6Al-4V alloy by cooling at different rates from the single beta-phase region into the two phase region. The effect of such morphologies on mechanical properties was studied using hot compression tests in a Gleeble thermomechanical simulator. A variety of complex morphologies could be obtained since the cooling rate has a significant influence on the beta to alpha phase transformation and the resulting morphological development. While most of the beta phase transformed to colonies of alpha at high cooling rates, it was possible to obtain a complex mixture of alpha colonies, grain boundary alpha and lamellar structure by decreasing the cooling rate. These complex morphologies each exhibited distinctive mechanical properties and characteristic dynamic phase transformation behaviour during deformation as a function of strain rate.