The influence of a dispersion of particles on the sintering of metal powders and wires

A dispersion of fine, stable particles is known to inhibit the sintering of metal powders and wires. This can be understood as an effect of the dispersed particles on the efficiency of the sources and sinks between which matter flows during sintering. Well-wetted particles cause the free surface of the metal containing them to become less effective as a source of matter because, as the surface recedes, particles are exposed and a new, high energy interface is created. Particles on grain boundaries, too, make the removal of matter from the boundary more difficult because they pin the boundary dislocations which (at a microscopic level) are the sites from which atoms are detached.The result is that sintering can proceed only if a threshold driving force is exceeded. This threshold depends on the size and volume fraction of particles; its magnitude is different for free surfaces and grain boundaries; and it may change as sintering proceeds. Because of this, some mechanisms of sintering—particularly those leading to desinfication—are inhibited more strongly than others.These ideas are developed quantitatively, and the results presented as sintering maps which show the degree to which each mechanism of sintering is inhibited. The predictions of the model are compared with the results of published experimental observations of inhibited sintering. There is broad agreement, though certain interesting discrepancies remain.