High-temperature plasticity in copper polycrystals

A procedure for testing and analysis is described that elicits the material parameters for deformation at elevated temperatures and at strain rates high enough to make diffusion an unimportant mechanism. As a first step, a simple scaling procedure is used on continuous stress strain curves to reduce the data to essentially one curve; the differentiated, normalized hardening diagram. A unique curve of this kind is then assumed at the microscopic level: it reflects the mechanism of hardening and dynamic recovery through dislocation storage and rearrangement. It can be integrated for arbitrary straining paths; initial texture and texture changes can be incorporated at this step; they may affect macroscopic behavior substantially. The dependence of the scaling parameters on temperature and strain rate can be well treated by thermal activation theory. It allows a condensation of temperature and strain rate into a single combined and normalized variable which may then be plotted against a normalized stress. The behavior on this reduced diagram does not necessarily obey a simple formula, but is is unique and allows extrapolation to temperatures and strain rates outside the range of measurements by interpolation on the reduced diagram. New data are presented for the deformation of pure copper polycrystals. 11 refs., 7 figs