LOW-CYCLE FATIGUE OF DISPERSION-STRENGTHENED COPPER

The cyclic deformation behavior of a dispersion-strengthened copper al loy, GlidCop Al-15, has been studied at plastic strain amplitudes in t he 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 dispe rsion-strengthened material exhibits a relatively stable cyclic respon se as a consequence of the dislocation substructures inherited from pr ior processing and stabilized by the Al2O3 particles. These dislocatio n 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 lifetim es of the dispersion-strengthened copper and the base alloy are simila r; however, the former is more susceptible to cracking at stress conce ntrations because of its substantially greater strength. This similari ty in fatigue lifetimes is a consequence of the dispersal of both defo rmation and damage accumulation by the fine grain size and dislocation /particle interactions in the GlidCop alloy. The operation of these me chanisms is reflected in the fine surface slip markings and rough frac ture surface-features for this material.