On the use of trace additions of Sn to enhance sintered 2xxx series Al powder alloys

The mechanical properties of a typical sintered aluminium alloy (Al–4.4Cu–0.8Si–0.5Mg) have been improved by the simultaneous use of trace additions of Sn, high sintering temperatures and modified heat treatments. Tin increases densification, but the Sn concentration is limited to ≤0.1wt% because incipient melting occurs during solution treatment at higher Sn levels. A sintering temperature of 620°C increases the liquid volume over that formed at the conventional 590°C sintering temperature. However, the higher sintering temperature results in the formation of an embrittling phase which can be eliminated if solution treatment is incorporated into the sintering cycle (a modified T5 heat treatment). These conditions produce a tensile strength of 375 MPa, an increase of nearly 20% over the unmodified alloy.