Sintering mechanisms of Armstrong prealloyed Ti-6Al-4V powders

The grain evolution and sintering mechanisms of Armstrong prealloyed Ti-6Al-4V powders have been investigated at different sintering temperatures and hold times. Theoretical sintered density is simulated using Coble׳s and Kang׳s densification equation controlled by lattice diffusion or boundary diffusion and compared with the experimental sintered density. Armstrong Ti-6Al-4V powder has an average grain size of 3 µm which benefits the grain boundary diffusion mechanism at the intermediate stage of sintering. Up to 900 °C and below 91% relative sintered density, boundary diffusion dominates sintering. Lattice diffusion dominates the densification process at higher temperature (1100-1300 °C). Armstrong Ti-6Al-4V powder sintered compacts show greater sintered density and better mechanical properties than HDH prealloyed Ti-6Al-4V powder compacts sintered under the same conditions. Sintering activation energies of both Armstrong Ti-6Al-4V powder and HDH Ti-6Al-4V powder were determined and they indicate the controlling sintering mechanism for Armstrong powder and HDH powder is lattice diffusion above 1040 °C and 1140 °C respectively.