CYCLIC PLASTIC STRAIN RESPONSE AND FRACTURE-BEHAVIOR OF AN OXIDE-DISPERSION-STRENGTHENED COPPER ALLOY

The cyclic stress response characteristics of an oxide-dispersion-strengthened copper alloy were studied over a range of plastic strains. The specimens were cycled using tension-compression loading under total strain control. In the as-rolled condition the dispersion-strengthened matrix displayed continuous softening to failure at all cyclic plastic strain amplitudes. The heat-treated material displayed initial hardening followed by softening to failure. Micromechanisms controlling the stress response during cyclic straining are highlighted and a rationale for the observed behaviour is discussed in terms of the concurrent and synergistic influences of the initial state of the matrix dislocation arrangement, multiple microscopic crack initiation and macrocrack growth. The kinetics of the cyclic fracture process of the oxide-dispersion-strengthened copper matrix are discussed in terms of the competing influences of intrinsic microstructural effects, plastic strain amplitude and concomitant response stress.