Trace additions of Sn, In, Bi, Sb and Pb have been used to activate the liq
uid phase sintering of an Al-4Cu-0.15Mg alloy. Additions of as little as 0.
05 wt% (similar to 0.01 at.%) increases the sintered density from 88 to 92%
of the theoretical density. The elements which aid sintering have both hig
h vacancy binding energies and high diffusivities in Al. It is suggested th
at the trace element diffuses into the Al, and forms trace element-vacancy
clusters. This reduces the diffusivity of the Cu in the Al matrix, delaying
Cu dissolution therefore causing the liquid to persist for longer times. T
his enhances sintering and therefore densification. (C) 1999 Acta Metallurg
ica Inc. Published by Elsevier Science Ltd. All rights reserved.