SENSITIVITY TO DYNAMIC STRAIN-AGING IN C-MN STEELS

In C-Mn steels and associated welds, the dynamic strain aging (DSA) ph enomenon induces an increase in the ultimate tensile strength, which i s associated with a ductility drop in the 100-200 degrees C temperatur e range (which can be an index of DSA sensitivity). Moreover, in the h eat-affected zone of the welds, the sensitivity to DSA, which is micro structure dependent, cannot be directly determined. Therefore, to stud y the effect of the microstructure on the DSA, internal friction tests combined with tensile tests were performed on various materials and m icrostructures (resulting from different quenching conditions), exhibi ting various DSA sensitivities. For these microstructures, the intensi ty of DSA, evaluated by the ductility loss, is proportional to the Sno ek peak height. Using the internal friction results (Snoek peak and as sociated cold work peak), the effect of microstructure on the DSA sens itivity can be interpreted in terms of the effect of the dislocation d ensity on the free interstitial content in the lattice.