Effect of annealing on the microstructure and texture of cold rolled CrCoNi medium-entropy alloy

摘要

The microstructure, texture and mechanical properties of medium-entropy ternary CrCoNi alloy after cold rolling and annealing were investigated. The cold rolled material shows a heavily fragmented microstructure coexisting with fine scale shear bands. The deformation texture is a a-fibre with a spread between the Goss and Brass component. This type of texture during cold rolling is direct evidence of a low stacking fault energy of the CrCoNi alloy. Annealing at 700 degrees C yields a fully recrystallized ultrafine grained microstructure with a large fraction of annealing twins. Annealing twins play a significant role in the evolution of the annealing texture. They lead to the emergence of new orientations which have first order twin relationship (60 degrees 111 rotation) with the alpha-fibre rolling texture components. Typical brass recrystallization texture BR {236} 385 component does not develop during recrystallization unlike in other low SFE alloys such as brass, Ag and Cu alloys. New prominent twin related orientations are retained with increasing annealing temperature due to the hindrance of preferential growth of certain crystallographic orientations. Tensile tests show that this alloy exhibits ultra-high strength and good ductility.