CREEP DEFORMATION OF DISPERSION-STRENGTHENED COPPER

The creep behavior of an internally oxidized, Al2O3 dispersion-strengt hened copper alloy, GlidCop Al-15, has been investigated in the temper ature range of 745 to 994 K. The results exhibit a high apparent stres s exponent (10 to 21) and a high apparent activation energy for creep (253.3 kJ/mole). To describe the creep behavior of this alloy, the Ros ler-Arzt model for attractive particle/dislocation interaction is appl ied. The results are in good agreement with the model when account is taken of the effects of the fine elongated grains and heavily dislocat ed structures revealed through transmission electron microscopy. The a nalysis demonstrates that the dislocation/particle interaction is of m oderate strength in this alloy, consistent with the observation that t he particle/matrix interface is partially coherent. In addition, the a nalysis reveals that the choice of mechanism and corresponding activat ion energy for vacancy diffusion has only a small effect on the calcul ated model parameters. It is argued that the weak dependence of subgra in size on stress demonstrates that creep deformation is particle cont rolled, rather than subgrain size controlled. In addition, the poorly developed subgrain structure and high dislocation densities are attrib uted to the presence of the fine oxide particles. Finally, the depende nce of rupture time on stress is shown to be consistent with a descrip tion of creep fracture based on diffusive cavity growth with continuou s nucleation.