Creep behavior of Fe-C alloys at high temperatures and high strain rates

The creep behavior of Fe-C alloys (1-1.8%C) has been studied at high temper atures (0.7-0.9T(m)) and high strain rates (1-100 s(-1)). The dominant defo rmation resistance has been found to be climb-controlled dislocation creep and thus the creep rates are a function of elastic modulus, lattice diffusi vity and stacking fault energy. The self-diffusion coefficient of iron in a ustenite was found to be solely a function of T-m/T and to vary as D = 6.8 x 10(-6) exp( - 17T(m)/T) m(2) s(-1). The Fe-C alloys were observed to have a high stacking fault energy which was unaffected by carbon and manganese. The stacking fault energy was observed to decrease with increasing concent rations of silicon, aluminum and chromium. At high stresses, deviation from power law behavior was accounted for by considering the contributions to d iffusivity by dislocation pipe diffusion. The results have been used to dev elop a rate equation for these steels of varying composition that depends o n only three material characteristics - alloy melting temperature, elastic modulus and stacking fault energy. (C) 2001 Elsevier Science B.V. All right s reserved.