Berlin 2015 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 35: Methods in Computational Materials Modelling IV: Steels

MM 35.3: Talk

Wednesday, March 18, 2015, 12:15–12:30, H 0106

Multi-scale description of super-saturated ferrite in severely deformed pearlitic wires — •Nematollahi Gh. Ali, Grabowski Blazej, Raabe Dierk, and Neugebauer Jörg — Max-Planck Institut für Eisenforschung, D-40237 Düsseldorf, Germany

Severely deformed pearlitic wires are the strongest structural materials with up to 7 GPa strength. Despite extensive research the fundamental mechanisms underlying the extraordinary strength are unclear. Experimental evidence suggests a substantial cementite decomposition resulting in a dramatically increased C concentration in the ferrite matrix which is 9 orders of magnitude above phase diagram predictions. To study the stability of C interstitials in ferrite and of C vacancies in cementite in the presence of elastic strain and dislocations we have developed a multi-scale approach using density functional theory, embedded atom potentials and an empirical model. A careful analysis reveals that a strain-induced stabilization of the C interstitial in ferrite in conjunction with a stabilization of the C trapping sides around dislocations enhance the carbon solubility strongly. Based on this insight we are able to explain the experimentally observed super-saturation of ferrite and the partial dissolution of cementite in severely deformed pearlite.