EFFECT OF ZINC CONTENT ON PROCESSING MAP FOR HOT DEFORMATION OF BETA-BRASS

The effect of zinc content on the processing map for hot deformation of beta-brass has been studied in the temperature range 550-800-degrees-C and strain rate range 0.001-100 s-1 in brasses containing 44, 47, 51 wt-%Zn. The three types of beta-brass exhibit superplastic deformation at temperatures of 550-800-degrees-C, less-than-or-equal-to 750-degrees-C, and 700-800-degrees-C, respectively, and at strain rates of < 1 s-1. In the 47%Zn beta-brass, superplasticity is curtailed at 800-degrees-C owing to abnormal grain growth caused by anomalous diffusion. In all three beta-brasses, superplastic deformation is dependent on the diffusion coefficient. At temperatures less than 700-degrees-C and in the strain rate range 0.01-1 s-1, the 51%Zn beta-brass exhibits a domain of dynamic recrystallisation caused by the presence of gamma-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.