EFFECT OF CERAMIC PARTICLE-SIZE, MELT SUPERHEAT, IMPURITIES AND ALLOYCONDITIONS ON THRESHOLD PRESSURE FOR INFILTRATION OF SIC POWDER COMPACTS BY ALUMINUM-BASED MELTS

An instrumented heated pressure vessel has been used to determine the effect of some experimental Variables on the pressurized infiltration of SiC powder preforms by a series of Al-based melts. Threshold pressu re for infiltration of 2014 Al alloy decreased with increasing SIC par ticle size and increasing melt superheat. Decreased purity of unalloye d aluminium and addition of 4.2 wt.% Cu to 99.999% pure aluminium incr eased the threshold pressure while addition of an extra 1.0 wt% Mg to 2014 alloy lowered it. increasing the melt superheat of 2014 alloy red uced the incidence of entrapped porosity in the compacts which tended to increase in the direction of infiltration. There was evidence of pa rtial dissolution of SiC into the liquid during infiltration. These fi ndings are discussed in the context of present understanding of metal matrix composite formation via melt infiltration routes.