The effect of trace elements on the sintering of an Al-Zn-Mg-Cu alloy

Trace elements can have a significant effect on the processing and properti es of aluminium alloys, including sintered alloys. As little as 0.07 wt% (1 00 ppm) lead, tin or indium promotes sintering in an Al-Zn-Mg-Cu alloy prod uced from mixed elemental powders. This is a liquid phase sintering system and thin liquid films form uniformly throughout the alloy in the presence o f the trace elements, but liquid pools develop in their absence. Analytical transmission electron microscopy indicates that the trace elements are con fined to the interparticle and grain boundary regions. The sintering enhanc ement is attributed to the segregation of the microalloying addition to the liquid-vapour interface. Because the microalloying elements have a low sur face tension, they lower the effective surface tension of the liquid. This reduces the wetting angle and extends the spreading of the liquid through t he matrix. An improvement in sintering results. (C) 2001 Acta Materialia In c. Published by Elsevier Science Ltd. All rights reserved.