Processing, microstructure and mechanical characterization of dispersion strengthened Cu-1%Y

Abstract

Dispersion strengthened Cu-1%Y (wt%) has been produced by mechanical alloying and subsequent consolidation by hot isostatic pressing (HIP). Samples of this alloy have been submitted to an equal channel angular pressing (ECAP) process and the effects on the microstructure and mechanical properties analyzed. The characteristics of the microstructure, such as the size distributions of both, the grains and Y-rich particles dispersed in the Cu matrix, have been studied by high resolution electron scanning microscopy and electron backscatter diffraction. The as-HIP alloy exhibits a quasi-bimodal distribution with an average diameter of 17 ± 14 μm. The ECAP treatment refines the average grain size to 1.3 ± 0.9 μm besides changing the size distribution of the Y-rich particles, which shifted from average size from 94 ± 9 nm to 55 ± 8 nm after ECAP. The mechanical characteristics have been investigated by means of microhardness measurements, and stress-strain tests in the temperature range 293 ― 573 K. The ECAP deformation resulted in an increase of the mechanical strength and a decrease in ductility. It is found that the Voce law can satisfactorily describe the plastic and hardening rate behavior of these alloys. The strain hardening rate plots as a function of flow stress for the samples tested at 293 ≤ T ≤ 773 K exhibited a two-stage behavior, comprising a transient stage at low stresses followed by the characteristic linear dependence for the stage III of hardening in f.c.c. metals.