M6 Sintering (Powder Metallurgy)

Topic

A powder compact of this metal, heated to a high temperature but without completely melting, densifies through the same atomic diffusion that another model of this set already establishes: it is the atoms of this metal, moving by this atomic diffusion between neighboring dust particles that still touch only at one point, which form, as described by Kuczynski's model, a neck of solid material that grows by uniting each pair of neighboring particles. The fact that this atomic diffusion is faster, at a higher temperature, means that, according to this same Kuczynski model, this growth of the neck between particles is also faster.

This same growth of the neck between particles, once each neck already solidly connects its neighboring particles, does not stop there, but continues during the intermediate stage densification of this dust compact: the necks between particles continue to grow and the network of pores that still separated these particles progressively closes, while the compact as a whole contracts and increases its density. That this growth of the neck between particles advances further, during this intermediate stage densification, causes the remaining pore network to close more, and the density of this compact, consequently, to be greater.

That is why this model, with the atomic diffusion and the growth of the neck between particles with which it was opened, describes the same mechanism of densification in the solid phase that already reuses, for the same purpose, another model of a different set of materials, the one that describes the sintering of a ceramic, although there this growth of the neck advances between ceramic particles instead of between metallic particles. That this same mechanism of densification by atomic diffusion is, in addition, the one that completely reuses, in its own words, another model of a still different set of materials, the one that describes a composite material of a particulate metal matrix that densifies instead by sintering in the liquid phase, makes that other model depend on this same growth of the neck between particles as its background densification mechanism, even when in that case it is the metal binder itself, molten, that acts as that phase. liquid.

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