Abnormal temperature effects on the dynamic yield stress of alpha-brass

The evolution of elastic-plastic wave in 70Cu-30Zn brass was measured so as to obtain information about its dynamic strength properties at normal and elevated temperatures. The different propagation velocities of plastic shock recorded in as-rolled and annealed brass can be explained in terms of a strong work-hardening. Measuring the decay of an elastic precursor wave revealed a transition from high-rate to low-rate mechanisms of plastic deformation. Unexpectedly, the flow stresses grow with increasing the temperature in both regimes. While at high strain rates this effect can be explained by phonon drag mechanisms, abnormal thermal hardening at a lower strain rate is apparently associated with different levels of short range order in the alloy at normal and elevated temperatures.