Liquid phase sintering of an AA2014-based composite prepared from an elemental powder mixture

Abstract

The AA2014 alloy reinforced with 10 vol% SiC particles has been prepared from elemental powders blended with the ceramic particles, instead of using a pre-alloyed atomized powder as the matrix material. Of critical importance in taking this uncommon processing route is liquid-phase sintering to transform the initial free aluminum and copper powder particles into the α-Al and the Θ-phase, thereby producing an integrated structure. The present investigation looked into the effect of sintering parameter on the microstructure and mechanical properties of the composite. It is shown that a sufficient time of sintering in the presence of a small volume fraction of the eutectic liquid must be given to dissolve the free copper particles in the α-Al solid solution. However, a prolonged sintering time will lead to the thickening of grain boundaries. A fast cooling after sintering is necessary to avoid the formation of a layered structure at grain boundaries as a result of local sequential solidification. With an adequate sintering scheme, the composite can be successfully fabricated to attain a strength of over 440MPa after the standard T6 heat treatment.