Microstructural evolution of Cr–Cu composites in liquid-phase sintering

The paper examines the effect of temperature and volume fraction of refractory particles on the kinetics of their growth during liquid-phase sintering of Cr–Cu composites in the temperature range 1150–1350°C under a vacuum of (2–4)∙10–3 Pa. It is established that the growth kinetics of average-size particles is described by a near-cubic law and the decrease in their number is determined by a near-inverse dependence: the apparent activation energy (Q = 113 ± 10 kJ/mol) is of the order of magnitude comparable to that of diffusion in liquid metals. According to the Lifshitz–Slyozov–Wagner theory (LSW theory), diffusion coalescence is indicative of diffusion-controlled particle growth. Experimental growth constants are one order of magnitude higher than those calculated within the classical LSW theory. The increase in the growth rate constant with volume fraction of refractory particles varying from 0.4 to 0.7 and the change in the particle size distribution function after sintering for 90 min at 1200°C agree with the Ardell model, which modifies the LSW theory considering the effect of volume fraction of particles on their growth kinetics.