Effect of zinc content on processing map for hot deformation of β brass

Abstract

The effect of zinc content on the processing map for hot deformation of β brass has been studied in the temperature range 550–800°C and strain rate range 0·001–100 s⁻¹ in brasses containing 44, 47, 51 wt-%Zn. The three types of β brass exhibit superplastic deformation at temperatures of 550–800°, ≤750°C, and 700–800°C, respectively, and at strain rates of <1 s⁻¹. In the 47%Zn β brass, superplasticity is curtailed at 800°Cowing to abnormal grain growth caused by anomalous diffusion. In all three β brasses, superplastic deformation is dependent on the diffusion coefficient. At temperatures less than 700°C and in the strain rate range 0·01−1 s⁻¹, the 51%Zn β brass exhibits a domain of dynamic recrystallisation caused by the presence of γ phase particles in the matrix. At higher strain rates (10 and 100 s⁻¹), the brasses become microstructurally unstable, which is manifested by oscillations in the stress–strain curves and by adiabatic shear bands and strain markings in the micrographs.

MST/1421