Effect of Mg as sintering additive on the consolidation of mechanically alloyed Al powder

Mechanically alloyed aluminium, MA Al powder particles are hard and covered by surface oxide layers. This gives problems in consolidation processing. Consolidation is often carried out by hot extrusion, as the main processing step. An alternative consolidation method consisting in a press-and-sinter process has been developed at the University of Seville. MA Al powder was prepared by attrition milling. To improve the sinterability of MA Al powder, small amounts of magnesium, ranging from 0.0 to 1.2 wt % Mg, were added after milling. The mixed powder was consolidated by cold pressing (1120 MPa) and vacuum sintering (650degreesC, 1h). Different mechanical and structural studies have been carried out. It has been observed that the addition of magnesium improves the mechanical properties of sintered MA Al. This is attributed to the reducing action of Mg on the Al sesquioxide layer and to the formation of liquid phases during sintering.