LOW-CYCLE FATIGUE OF DISPERSION-STRENGTHENED COPPER

The cyclic deformation behavior of a dispersion-strengthened copper alloy, GlidCop Al-15, has been studied at plastic strain amplitudes in the range 0.1 pet less than or equal to Delta epsilon(p)/2.4 less than or equal to 0.8 pet. Compared to pure polycystalline copper, the dispersion-strengthened material exhibits a relatively stable cyclic response as a consequence of the dislocation substructures inherited from prior processing and stabilized by the Al2O3 particles. These dislocation structures remain largely unaltered during the course of deformation; hence, they do not reveal any of the features classically associated with copper tested in fatigue. At low amplitudes, the fatigue lifetimes of the dispersion-strengthened copper and the base alloy are similar; however, the former is more susceptible to cracking at stress concentrations because of its substantially greater strength. This similarity in fatigue lifetimes is a consequence of the dispersal of both deformation and damage accumulation by the fine grain size and dislocation/particle interactions in the GlidCop alloy. The operation of these mechanisms is reflected in the fine surface slip markings and rough fracture surface-features for this material.