Influence of alloying elements on the strain rate and temperature dependence of the flow stress of steels

After a short introduction to the theoretical background of thermally activated glide of dislocations, a constitutive model is presented, which describes the temperature and strain-rate dependence of the flow stress. The properties of this constitutive equation were estimated for several plain carbon steels in normalized conditions, for quenched and tempered low-alloy steels, as well as for some high-strength low-alloy (HSLA) steels based on the temperature dependence and strain-rate sensitivity of the flow stress at temperatures 81 K less than or equal to T less than or equal to 398 K and strain rates 5 . 10(-5) s(-1) less than or equal to epsilon less than or equal to 1 . 10(-2) s(-1). The constitutive equation enables the extrapolation of flow-stress data to higher strain rates (epsilon less than or similar to 10(+4) s(-1)), which are in good agreement with the results obtained from high strain-rate deformation tests. The influence of solute-alloying elements on the thermal stress, the activation enthalpy, and the constitutive parameters will be discussed.