Flow Stress and Ductility of Brass with Various Zn-Content at Wide Range of Strain Rate

Tension tests were performed on five α-brasses with 1 to 30-wt.% Zn, 60-40 brass and OFHC copper at a wide range of strain rates of 2.2×10-4 to 2.1×102s-1. The strain-rate sensitivity to flow stress in α-brasses reduces with increasing Zn-content, and almost no strain-rate effect is found in 70-30 brass. The fracture elongation, which strongly depends on the uniform elongation, increases with increasing Zn-content, whereas the reduction of area slightly decreases with Zn-content. The n-value in the Hollomon-type constitutive equation, which governs the uniform elongation, becomes smaller at the strain region just before the onset of local necking. To describe the above-mentioned mechanical properties, the Ludwik-type costitutive equation with the power law of strain-rate sensitivity: σ=(σ0+Cεn)εm, is proposed, in which two sets of material constants σ0, C and n should be determined for two different strain regions.