Hydrodynamical behaviour of a two-phase superplastic alloy: α/β brass

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Abstract
Constitutive laws hitherto applied to two-phase superplastic alloys have not taken into account their two-phase nature. In order to determine the influence of each of the phases on the constitutive laws, α/β brass was studied for different phase fractions and at different temperatures. A constitutive law is found in which the strain rate is proportional to the strain rate of the softer β phase, the constant of proportionality being a rapidly decreasing function of the α-phase fraction. Thus analysed, the behaviour of this superplastic alloy resembles that of a two-phase fluid consisting of hard particles in a viscous non-Newtonian material. This similarity agrees with observations in superplastic materials, i.e. rotation of hard phases, differences in texture evolutions, and sliding along interfaces.