Thermodynamics of carbon solubility in ferrite and vacancy formation in cementite in strained pearlite

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• 作者：Gh. Ali Nematollahi ; ^{a.nematollahi@mpie.de} ; Johann von Pezold ; Jö ; rg Neugebauer ; Dierk Raabe
• 关键词：Density-functional theory ; Ferrite ; Cementite ; Carbon interstitial ; Vacancy formation energy
• 刊名：Acta Materialia
• 出版年：2013
• 出版时间：March, 2013
• 年：2013
• 卷：61
• 期：5
• 页码：1773-1784
• 全文大小：1K

文摘

In order to investigate the thermodynamic driving force for the experimentally observed accumulation of C in ferritic layers of severely plastically deformed pearlitic wires, the stabilities of C interstitials in ferrite and of C vacancies in cementite are investigated as a function of uniaxial stain, using density-functional theory. In the presence of an applied strain along [1 1 0] or [1 1 1], the C interstitial in ferrite is significantly stabilized, while the C vacancy in cementite is moderately destabilized by the corresponding strain states in cementite [1 0 0] and ([0 1 0]). The enhanced stabilization of the C interstitial gives rise to an increase in the C concentration within the ferritic layers by up to two orders of magnitude. Our results thus suggest that in addition to the generally assumed non-equilibrium, dislocation-based mechanism, there is also a strain-induced thermodynamic driving force for the experimentally observed accumulation of C in ferrite.