Strain Rate Dependency of Dynamic Flow Stress of Iron in Wide Strain Rate Range

Abstract

Constant strain rate tests are made on iron in a strain rate range from about 1×10^-3 to 2×10⁴/sec at temperatures of 293K, 208K and 79K. At high strain rates, decremental strain rate tests are also performed. In order to evaluate the strain rate dependency of the dynamic flow stress over the wide strain rate range, activation energy E (τ) for deformation of pure iron obtained by Aono et al. is used. The deformation mechanism is controlled mainly by a thermally activated process of a formation of kink pairs, however below the strain rate of about 1/sec at 293K, it seems to be controlled by the thermally activated process of interaction of moving dislocations with forest ones.