Influence of powder shape on atomic diffusivity and resultant densification mechanisms during spark plasma sintering

During spark plasma sintering (SPS), the gas atomized powders experience a sequence of densification mechanisms of particle arrangement, viscous flow, and high temperature creep concurrent with grain growth. However, after short time ball-milling of the original powders, the dramatic change of powder shape affects the thermodynamics (densification mechanisms) and kinetics (mass transfer) of powder densification based on the evolution of characteristic microstructure and densification data. In addition, we establish a theoretical framework to determine an atomic diffusivity D-T, by incorporating the contribution of the applied pressure to the densification kinetics. Furthermore, the D-T can be utilized to govern powder densification during SPS. Accordingly, a larger D-T associated with the irregular metallic glass powder gives rise to faster powder densification, as compared with the original spherical powder without mechanical milling. (C) 2019 Elsevier B.V. All rights reserved.