Processing maps for hot working of Cu-Ni-Zn alloys

Abstract

The constitutive behaviour of α-β nickel silver in the temperature range 600–850 °C and strainrate range 0.001–100s⁻¹ was characterized with the help of a processing map generated on the principles of the dynamic materials model. On the basis of the flow-stress data, processing maps showing the variation of the efficiency of power dissipation (given by [2m/(m+1)], wherem is the strain-rate sensitivity) with temperature and strain rate were obtained, α-β nickel silver exhibits a single domain at temperatures greater than 700 °C and at strain rates lower than 1 s⁻¹ with a maximum efficiency of power dissipation of about 42% occurring at about 850 °C and at 0.1 s⁻¹. In the domain, the α phase undergoes dynamic recrystallization and controls the deformation of the alloy, while the β phase deforms superplastically. Optimum conditions for the processing of α-β nickel silver are 850 °C and 0.1 s⁻¹. The material undergoes unstable flow at strain rates of 10 and 100 s⁻¹ and in the temperature range 600–750 °C, manifestated in the form of adiabatic shear bands.