Microband-induced plasticity in a Ti-rich high-entropy alloy

Abstract

Abstract Microstructure evolution and mechanical behavior of an Al4Mo4Nb8Ti50Zr34 high-entropy alloy were studied. In the as-cast condition, the alloy had a single-phase weakly B2 ordered bcc structure with a grain size of 100 ± 50 μm. The microstructure evolution during cold rolling to 90% thickness strain was initially associated with the development of substructure in the form of slip bands and then the formation of deformation bands propagating through several grains. Annealing of the cold-rolled alloy at T ≥ 700 °C resulted in the formation of a recrystallized microstructure with grain sizes varying from ∼6 μm after annealing at 600 °C to ∼250 μm at 1000 °C. A small fraction of tiny oxides was observed in the alloy annealed at 700 °C; the particles did not influence noticeably on the alloy properties. In spite of lack of work hardening in both the as-cast and recrystallized conditions, the alloy demonstrated the yield strength of 825–910 MPa and elongation to fracture of 11.5–15.2%. This behavior can be associated with strain localization due to the formation of dislocation microbands in the weakly B2 ordered bcc matrix.