First-principles study of carbon segregation in bcc iron symmetrical tilt grain boundaries

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• 作者：Jingliang Wang ^{jingliang.wang@rub.de" class="auth_mail" title="E-mail the corresponding author} ; Rebecca Janisch ^{rebecca.janisch@rub.de" class="auth_mail" title="E-mail the corresponding author} ; Georg K.H. Madsen ^{georg.madsen@rub.de" class="auth_mail" title="E-mail the corresponding author} ; Ralf Drautz ; ^{ralf.drautz@rub.de" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Grain boundary segregation ; Grain boundary cohesion ; First-principles calculation ; Atomic structure ; Steel
• 刊名：Acta Materialia
• 出版年：2016
• 出版时间：15 August 2016
• 年：2016
• 卷：115
• 期：Complete
• 页码：259-268
• 全文大小：1329 K

文摘

Segregation of light elements can profoundly affect the energies and cohesive properties of grain boundaries. First-principles calculations have been performed to determine the carbon solution energies and cohesive properties of three different grain boundaries in presence of carbon. It is demonstrated that the most stable segregation sites possess the greatest coordination number and maximum Fe–C nearest neighbor distance. Thereby a geometric criterion for predicting the segregation sites is suggested. Open grain boundary structures are shown to be more attractive to C atoms than the compact grain boundary structure, vacancies and dislocations, and C segregation at open grain boundaries decreases the grain boundary energy. The theoretical fracture strength of grain boundaries increases with C concentration and tend to similar values for certain areal concentrations irrespective of the grain boundary structures. This implies that the maximum fracture strength of a grain boundary depends on the maximum C areal concentration it can accommodate.