Segregation assisted microtwinning during creep of a polycrystalline L1₂-hardened Co-base superalloy

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• 作者：Lisa P. Freund^a ; ^{lisa.freund@fau.de" class="auth_mail" title="E-mail the corresponding author} ; Olivier M.D.M. Messé ; ^b ; Jonathan S. Barnard^b ; ¹ ; Mathias Gö ; ken^a ; Steffen Neumeier^a ; Catherine M.F. Rae^b
• 关键词：Cobalt-base superalloys ; Creep ; Microtwinning ; Stacking faults ; Transmission electron microscopy
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：15 January 2017
• 年：2017
• 卷：123
• 期：Complete
• 页码：295-304
• 全文大小：4106 K

文摘

A polycrystalline L1₂-hardened Co-base superalloy was creep deformed at 750 °C. The investigation of the deformed microstructure in the transmission electron microscope revealed microtwinning to be the prevailing deformation mechanism. The detected twins spanned the entire grain and cut through both, γ and γ′. Detailed high-resolution transmission electron microscopy investigations indicated that twin growth takes place by the slip of single a/6 〈112〉 partial dislocations along the twin boundary. Further analysis of the twin boundaries in the γ′ phase revealed segregation of elements known to decrease the stacking fault energy and a local depletion of γ′ forming elements. We propose that this segregation behavior enables subsequent a/6〈112〉 dislocations to easily slip along the twin boundary and further thicken the twins in the process.