Enhanced densification of cavitated dispersion-strengthened aluminum by thermal cycling

We report experimental data of creep cavity shrinkage for dispersion-streng thened-cast aluminum with about 23 vol pet submicron Al2O3 dispersoids, ann ealed isothermally or subjected to thermal cycling without applied stress. Thermal cycling is found to increase the rate of densification by a factor of 3 to 5.5 relative to isothermal annealing at the upper cycling temperatu re, allowing for recovery of full theoretical density in a shorter time. Is othermal densification is discussed in light of a diffusive cavity shrinkag e mechanism, and a model considering thermal mismatch stresses is employed to rationalize the enhanced rate of densification observed during thermal c ycling. Intermittent thermal-cycling densification is shown to improve cree p life of dispersion-strengthened aluminum through the suppression of terti ary damage accumulation processes.