Fabrication and characterization of dispersion strengthened Cu-0.8%Y

Two batches of dispersion strengthened copper alloys with a nominal composition Cu-0.8 wt%Y have been obtained following different powder metallurgy routes that include sintering by hot isostatic pressing and subsequent thermomechanical treatments. One batch, named Cu-0.8Y, was produced by sintering the raw prealloyed powder. To promote the formation of Y2O3 nanoparticles by internal oxidation and refine the reinforcing particle dispersion, the other batch, Cu-0.8 YM, was produced from milled prealloyed powder. Both alloys were subjected to equal channel angular pressing (ECAP) for refining their microstructure. Nanoparticles of different nature were found in the alloys: Y-rich particles in the Cu-0.8Y matrix and Y-O rich particles in the Cu-0.8 YM. In both alloys the equal channel angular pressing treatment gives place to a significant refinement of the microstructure, which exhibited a sub-micrometer grain size distribution. The mechanical properties were studied from microhardness measurements, and tensile tests in the temperature range 293-773 K. The microhardness values of the alloys remained constant over the entire temperature range, presenting Cu-0.8 YM a higher value. The thermal behavior of the stress-strain curves of as HIP materials follows the expected for FCC metals. The ECAP processed materials show a work hardening region shorter than that of the non-processed materials. Besides, the tensile curves and microhardness values reveal a softening of these materials above 573 K due to dynamic recrystallization phenomena, with a complete recrystallization between 623-773 K. The Voce model and Kock-Mecking approach have been applied to analyze the stress-strain curves.