STRAIN-RATE AND TEMPERATURE-DEPENDENCE OF THE TENSILE FLOW-STRESS OF HIGH-PURITY ALPHA-IRON ABOVE 250-K (REGIME I) STUDIED BY MEANS OF STRESS-RELAXATION TESTS

The dependence of the flow stress of high-purity alpha-iron monocrystals on temperature and strain rate, measured by successive tensile deformations at temperatures between 250 and 340 K and correlated stress-relaxation tests, is analysed by means of Seeger's theory of thermally activated kink-pair formation in screw dislocations. The so-called elastic-interaction approximation applies excellently to the experimental data, particularly to those on the dependence on strain rate, which was varied by a factor of up to 1000. Several characteristic kink and dislocation parameters, including the kink diffusivity, can be evaluated quantitatively. The numerical value of the kink height indicates unambiguously that the kink formation occurs on {112} planes.