IN-SITU SYNTHESIS OF TIC PARTICULATE-REINFORCED ALUMINUM-MATRIX COMPOSITES

Particulate TiC-reinforced aluminum composite specimens were processed by compacting a mixture of titanium, carbon, and aluminum powders into preforms that were infiltrated with molten aluminum and subsequently heated in a differential thermal analyzer to about 1573 K under argon atmosphere, The onset of formation of TiC particles began at about 1150 K by reaction of TiAl3 with Al4C3. Subsequent formation of TiC particles at higher temperatures to approximately 1265 K occurred by direct reaction of carbon with TiA1(3). Above this temperature, the TiC particles coarsened with increasing temperature from an initial size of about 0.15 mu m. TiC particles were also produced in preforms that were not infiltrated; however, the presence of liquid aluminum in infiltrated specimens inhibited particle agglomeration and sintering. Infiltrated preforms could, therefore, serve as excellent ''master alloys'' for subsequent dilution in an aluminum melt and processing of metal-matrix composites (MMCs) reinforced with submicron TiC particulates.