FLEXURE STRENGTH OF MELT-INFILTRATION-PROCESSED TITANIUM CARBIDE NICKEL ALUMINIDE COMPOSITES

TiC/Ni3Al composites were prepared using a simple melt-infiltration pr ocess, performed at either 1300 degrees or 1400 degrees C, with the Ni (3)AI content varied over the range of 8-25 vol%, Densities >96% of th eoretical were obtained for all composites. Four-point flexure strengt hs at 22 degrees C increased as the Ni(3)AI content increased (i.e., s imilar to 1100 MPa at 20 vol% Ni(3)AI), with the highest strengths bei ng observed for composites processed at 1300 degrees C, because of red uced TiC grain size. Strengths at elevated temperatures increased with test temperature, up to similar to 1000 degrees C, As with the yieldi ng behavior of the Ni,AI alloy used, a maximum in composite strength ( similar to 1350 MPa) versus temperature was observed; this occurred at 950 degrees C, which is similar to 300 degrees C above the yield maxi mum for the alloy. Extensive plastic strain was achieved in the compos ites even at high loading rates at 1135 degrees C, and the yield stres s was dependent on the applied loading rate.