Abstract
The Stage I work-hardening behaviour of disordered Cu3Au single crystals containing volume fractions, f, of SiO2 particles equalling 0·005 and 0·01, oriented for single slip on (111)[101], was studied in compression at 77 K and 295 K. At 295 K, Lüders-band propagation was found to obscure the work-hardening behaviour up to about 10% shear strain. The rest of Stage I is parabolic when f = 0·01 but not when f = 0·005. At 77 K, only the samples with f = 0·01 showed any real evidence of parabolic hardening. Additional experiments demonstrated that no recovery of the flow stress is observed, which is attributed to the resistance of these alloys to plastic relaxation by static recovery processes. The experimentally measured work-hardening rates in the parabolic region of Stage I are in reasonable agreement with the quantitative predictions of the theories of Brown, Stobba and co-workers (theory B) and Hirsch, Humphreys and co-workers (theory H). The microstructures of samples with f = 0·01, deformed at 295 K to shear strains of 0·05, 0·1 and 0·2, were studied by transmission electron microscopy. The structures observed are similar to those seen in other oxide dispersion-strengthened alloys, and contain primary prismatic dislocation loops, helices, voids and extensive arrays of dislocation dipoles in samples deformed to 10% shear strain. A three-dimensional network of secondary dislocations is formed around practically every particle in samples deformed to 20% shear strain. It is argued that the microscopic evidence marginally favours theory B over theory H.
