The effect of trace additions of magnesium on the sintering of aluminum and
its alloys is examined. Magnesium, especially at low concentrations, has a
disproportionate effect on sintering because it disrupts the passivating A
l2O3 layer through the formation of a spinel phase. Magnesium penetrates th
e sintering compact by solid-state diffusion, and the oxide is reduced at t
he metal-oxide interface. This facilitates solid-state sintering, as well a
s wetting of the underlying metal by sintering liquids, when these are pres
ent. The optimum magnesium concentration is approximately 0.1 to 1.0 wt pet
, but this is dependent on the volume of oxide and, hence, the particle siz
e, as well as the sintering conditions. Small particle-size fractions requi
re proportionally more magnesium than large-size fractions do.