Mane, Rahul B and Panigrahi, Bharat Bhooshan
(2018)
Comparative study on sintering kinetics of as-milled and annealed CoCrFeNi high entropy alloy powders.
Materials Chemistry and Physics, 210.
pp. 49-56.
ISSN 0254-0584
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Abstract
This work attempts to understand the effect of initial conditions, i.e., as-milled powder and phase stabilized nearly single phase powder (through annealing), on sintering kinetics of CoCrFeNi high entropy alloy powders. Dilatometric study indicates, axial shrinkage reduced from about 5% to 3% when powder was annealed. Analysis of shrinkage through non-isothermal method shows activation energies of sintering increased significantly for a given model, in annealed powder compared to as-milled powder. Calculated activation energies indicate, in as-milled powder grain boundary diffusion seems to be the dominating mechanism, attributed to the presence of ultrafine grains and a large fraction of grain boundaries. On the other hand, annealing helped to form almost single phase HEA, decrease in defect concentration and reduced grain boundary fraction with increased crystallites; which led to increase in activation energies. Coefficients of thermal expansion have also been studied and it was found to vary with temperature range.
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