Sensitivity to dynamic strain aging in C—Mn steels

International audienceIn C-Mn steels and associated welds, the dynamic strain aging (DSA) phenomenon induces an increase in the ultimate tensile strength, which is associated with a ductility drop in the 100–200 °C temperature range (which can be an index of DSA sensitivity). Moreover, in the heat-affected zone of the welds, the sensitivity to DSA, which is microstructure dependent, cannot be directly determined. Therefore, to study the effect of the microstructure on the DSA, internal friction tests combined with tensile tests were performed on various materials and microstructures (resulting from different quenching conditions), exhibiting various DSA sensitivities. For these microstructures, the intensity of DSA, evaluated by the ductility loss, is proportional to the Snœk peak height. Using the internal friction results (Snœk peak and associated cold work peak), the effect of microstructure on the DSA sensitivity can be interpreted in terms of the effect of the dislocation density on the free interstitial content in the lattice