CHARACTERIZATION OF METAL MATRIX COMPOSITES FABRICATED BY VACUUM INFILTRATION OF A LIQUID-METAL UNDER AN INERT-GAS PRESSURE

Silicon carbide whisker-reinforced aluminium was fabricated by vacuum infiltration of liquid aluminium into a porous whisker preform under an argon gas pressure, using an infiltration temperature of 665-degrees-C. The volume fraction of whiskers ranged from 11% to 37%. No whisker pull-out was observed on the fracture surface for an infiltration temperature of 665-degrees-C, but some whisker pull-out was observed for an infiltration temperature of 720-degrees-C. Both the tensile strength and ductility decreased with increasing infiltration temperature above 665-degrees-C. Tensile test results from room temperature to 300-degrees-C are reported. They showed that the quality of these composites was comparable to that of composites made by powder metallurgy of squeeze casting. The coefficient of thermal expansion at 100-150-degrees-C was decreased by 45% by the addition of 37 vol % whiskers.