Novel oxide-dispersion-strengthened copper alloys from rapidly solidified precursors: Part 2. Creep behavior

Yttria- and zirconia-dispersion-strengthened copper alloys produced by hot pressing and hot extrusion of internally oxidized melt-spun Cu-0.33 at. pct Y and Cu-0.32 at. pct Zr ribbons were subjected to compressive creep tests at 923 and 973 K. Creep strengths and stress exponents were higher for the Cu-ZrO2 alloy than for Cu-Y2O3, and both were higher than those of pure copper. Comparisons of the creep properties with published data for pure copper along with microscopic evidence indicated that at least two creep mechanisms were operating in these alloys. These are attractive dislocation/particle interactions in the matrix and particle-inhibited diffusional creep. The experimental data at low stresses could be described reasonably well by the Arzt-Ashby-Verrai model for particle-restricted diffusional creep, using plausible values for the structure-related parameters. Fitting the higher stress creep data to the Rosier-Arzt model of dislocation/particle interaction resulted in values of the relaxation parameter (k) within the bounds predicted by the theory. The estimated k values for Y2O3 and ZrO2 are in the vicinity of ∼0.8, compared with ∼0.9 for the γ-Al2O3 dispersoids in conventional oxide-dispersion-strengthened (ODS) Cu. The analysis suggests that these alternate dispersoids with fluorite-related structures may interact more effectively with dislocations during creep.