Ravi Sankar Kottada

Evaluation of the diffusion coefficient of metal powders was attempted by using the power-law creep model in conjunction with the isothermal densification kinetics during spark plasma sintering (SPS). The diffusion coefficients obtained from the densification data of elemental Fe, Ni and Al powders are found to be higher than those reported in the literature. The higher values of diffusivity can be attributed to electric current effects. Our analysis demonstrates that it is possible to evaluate diffusion coefficients from experimental SPS densification data.

Joule heating as a primary heating source mechanism was probed during spark plasma sintering (SPS) of pure metal powders (Fe, Ni and Cu). Resistance to electric path was estimated from voltage-current measurements obtained online during these experiments. Resistance was observed to saturate at the same value irrespective of the type of metal powder, after attaining a sintering temperature of ∼0.3Tm. This saturation in resistance is attributed primarily to the Joule heating that occurs at the graphite-foil and punch in an SPS system.

The densification kinetics during spark plasma sintering (SPS) of FeAl and NiAl powders were analyzed using a model proposed by Bernard-Granger and Guizard [10]. Creep parameters obtained through densification data are in good agreement with those obtained from conventional creep experiments. Validity of the model was illustrated for aluminides in the form of deformation mechanism maps. This validation assures plausible confidence to predict creep behavior using densification data obtained during pressure assisted sintering of metallic alloys.