HIGH-TEMPERATURE SLOW-STRAIN-RATE COMPRESSION STUDIES ON COAL-TIB2 COMPOSITES

CoAl-base composites containing various volume fractions of TiB2 particulates in the 1 to 3-μm size range were tested in compression over a range of strain rates at 1100 to 1300 K. Hotpressed and postcompression microstructures were characterized using optical and transmission electron microscopy. For a strain rate of 2 × 10-6 s-1, the flow stress at 1300 K of CoAl-20 vol pct TiB2 was twice that of monolithic CoAl. Correspondingly, the stress exponent of CoAl-20 vol pct TiB2 at 1300 K was ∼4.5 compared to ∼3.0 for stoichiometric monolithic CoAl. This increased resistance of the composite to deformation at elevated temperatures is attributed to TiB2 particulate-dislocation interactions. The high-temperature compressive deformation behaviors of NiAl-TiB2 and CoAl-TiB2 composites are compared. © 1990 The Metallurgical of Society of AIME.