Modeling of hot isostatic pressing and hot triaxial compaction of Ti–6Al–4V powder

The accuracy of a hybrid continuum–micromechanical model for predicting the rate-dependent consolidation of metal powder was established using measurements from hot isostatic pressing (HIP) and hot triaxial compaction (HTC) experiments. The experiments were performed with PREP® Ti–6Al–4V powder encapsulated in thin-walled containers and yielded relative density vs time and height vs relative density data for direct comparisons with model predictions. The model was found to underpredict the densification rate in HIP, primarily during the early stages of consolidation, and the degree of consolidation during HTC. Adjustments to the values of the strain-rate sensitivity or a state variable representing the geometric structure of powder compacts resulted in good agreement between hybrid model predictions and measurements. The physical basis for discrepancies between predictions and measurements and justification for the postulated/required parameter adjustments were attributed to two factors: (1) differences in microstructure between the unconsolidated powder and the fully consolidated material used in the compression testing to obtain the material coefficients for the model; and (2) interparticle bonding characteristics/particle sliding effects not taken into account in determining the material properties for the model.