Effect of twin spacing, dislocation density and crystallite size on the strength of nanostructured α-brass

• Nanotwinned α-brass with varying lamellae thickness (28–170 nm), has been produced by cryorolling.
• Equal thickness and uniform distribution of nanotwins increase the hardness homogeneity.
• Formation of ∼10 nm subgrains within preexisting twin lamellae causes the refinement.
• Flow stress has been predicted considering dislocation density, twin spacing and crystallite size.

Nanotwinned α-brass (Cu–30 wt.% Zn) with varying lamellae thickness in the range of 28–170 nm, has been produced by cryorolling (CR). The effect of CR strain (ɛCR = 0.2–0.95) on the evolution of homogeneity and refinement in terms of twin lamellae thickness, twin spacing, and their distribution, have been studied using high-resolution transmission electron microscopy (HRTEM) and microhardness measurements. Analysis of X-ray peak broadening has shown that the crystallite size reduces down to 20 nm at ɛCR = 0.95, which scales with the subgrain size in preexisting twin lamellae, as revealed under HRTEM. The effect of dislocation density and crystallite size on the strength of nanotwinned brass has been correlated using an analytical model.