ELEVATED-TEMPERATURE MECHANICAL-BEHAVIOR OF COSI AND PARTICULATE-REINFORCED COSI PRODUCED BY SPRAY ATOMIZATION AND CODEPOSITION

Monolithic CoSi and TiB2 reinforced CoSi materials were produced by sp ray atomization and co-deposition. The creep behavior of both material s at elevated temperature was investigated. The unreinforced material of grain size approximate to 25 mu m exhibited a stress exponent of th ree, activation energy for creep of 320 kJ/mole, dislocation substruct ure of homogeneously distributed dislocations, and inverse creep trans ients upon stress increases. These results suggest that the creep beha vior of CoSi is controlled by a dislocation glide mechanism. In contra st, the reinforced material of a finer grain size (approximate to 10 m u m) exhibited a stress exponent of unity, activation energy for creep of 240 kJ/mole, and negligible creep transients upon stress increases , suggesting that the creep behavior of the reinforced material is con trolled by a diffusional creep mechanism. The creep resistance of the reinforced material was lower than that for the unreinforced material. This is a result of the finer grain size and higher porosity in the r einforced material.