STEADY-STATE CREEP-BEHAVIOR OF AN AL-AL2O3 ALLOY

The Al-Al2O3 alloy produced by powder metallurgy route has been tested under compression creep in the temperature range 573-723 K to evaluat e the steady-stale creep mechanisms. The steady stale creep data cover ing almost five orders of magnitude in creep rate shows two distinct r egimes of creep deformation at all the temperatures. In the high stres s regime (region-II), the creep data shows high and variable apparent stress exponents, 25-30 and high apparent activation energy, 372 kJ/mo l. However, in the low stress regime (region-I), the lower values of s tress exponents, 7-11 and activation energy, 85 kJ/mol are observed. T he TEM micrographs of the uncrept and crept specimens exhibit subgrain s with Al2O3 particles lying on the subgrain boundaries. The high stre ss regime data was examined in terms of pipe-diffusion controlled cons tant substructure creep model and thermally activated detachment contr olled dislocation creep model. The detachment controlled dislocation m odel can describe the present data more successfully. The low stress r egime data was analyzed according to the thermally activated detachmen t controlled diffusional creep model and pipe-diffusion controlled str ess dependent substructure model. Thermally activated detachment contr olled diffusional creep mechanism appears to be more appropriate for t he present data.