An analysis of cavity growth during open-die hot forging of Ti-6Al-4V

Abstract

The effect of local deformation conditions on the cavitation behavior of Ti-6Al-4V during open-die forging was quantified using optical metallography and continuum finite-element-method (FEM) analysis of pancake forgings. The observations were interpreted using meso- and microscopic-scale models, which were used to predict the average cavity size as well the size of the largest cavities. The mesoscale model gave excellent predictions of the average cavity size at different locations of the workpiece, but grossly underestimated the size of the largest cavities by an order of magnitude. On the other hand, the micromechanical model, which accounted for the effect of local colony orientation on cavity growth, was capable of predicting the size of the largest cavities very well. Because the large cavities are the most deleterious with respect to subsequent processing and service performance, it was concluded that micromechanical models should be used to design primary hot working processes in order to minimize the size and number of such cavities.