Observations on the Stress-Dependence of Steady-State Creep of a Dispersion-Strengthened Alloy

The stress-dependence of steady-state creep in drawn wires of nickel–thoria dispersion-strengthened alloys has been examined under conditions where direct particle-strengthening is operative. A series of alloys was chosen in which the interparticle spacing was varied from ∼ 7 to 0·37 μm at a constant particle size of 0·11 μm. Isothermal creep tests were performed on these alloys in vacuum at 0·70 and 0·80 T _m . It is proposed that the stress-dependence term in creep is related to an effective stress acting on a Frank-Read type source; this accounts for the 10² difference between the observed steady-state creep rate and that predicted by existing theories, while the activation energy for the creep process is almost equal to that for nickel self-diffusion.