Enhancement of Diffusion Coefficients in Ti-Mo Alloy by the Spark Plasma Sintering/Field Assisted Sintering Technology

The enhancement of interdiffusion coefficients in bulk Ti-Mo alloy system by the SPS/FAST process was investigated at 1000°C for 8hrs and at 1200°C for 4hrs. During annealing, the current density of the SPS was maintained at an RMS of 188 A/cm 2 for the sample annealed at 1000°C and 177 A/cm 2 for the sample annealed at 1200°C and the average heating rate was 200 K/min. The elemental concentration of Ti and Mo across the interdiffusion region was measured using electron probe microanalyzer (EPMA) and the resulting concentration vs distance profiles applied in evaluating the interdiffusion coefficients using the Den-Broeder and the analytical methods. The interdiffusion coefficients calculated using the two methods were then compared in order to ensure accuracy and reliability. Possible enhancement of the diffusion process in SPS was established by comparing interdiffusion coefficients obtained from SPS annealing to those obtained from the literature for the same alloy and annealing temperature but for which no electric current was flowing through the sample. The results showed that interdiffusion coefficients evaluated using the Den-Broeder method were closely similar to those evaluated using the analytical method. The results also showed that the interdiffusion coefficients measured in the presence of an electric current were significantly higher than those obtained from traditional annealing methods. This enhancement can be attributed to increased vacancy concentration and defect mobility facilitated by the electric current while flowing through the Ti-Mo sample.