Dynamic strain ageing in iron alloys: The shielding effect of carbon

Dynamic strain ageing in iron due to various interstitial (carbon) and substitutional (nickel, silicon, chromium, aluminum) solute atoms has been studied by in situ straining in a transmission electron microscope. The effect of carbon in solid solution is characterized by two different carbon-dislocation interactions in the jerky flow and serrated flow temperature domains, and by a low mobility of screw dislocations controlled by a "high-temperature Peierls mechanism". Substitutional atoms in solid solution can either move the domain of dynamic strain ageing to higher temperatures or not, depending on their chemical affinity for carbon. The results are interpreted by a shielding effect of mobile carbon atoms, inhibiting the interaction between dislocations and substitutional solute atoms.