纳米压痕 纯铁 氢 硬度 位错.pdfVIP

Available online at Acta Materialia 58 (2010) 5274–5285 /locate/actamat Recent developments in the study of hydrogen embrittlement: Hydrogen effect on dislocation nucleation Afrooz Barnoush *, Horst Vehoff Saarland University, Department of Materials Science, Bldg. D22, P.O. Box 151150, D-66041 Saarbruecken, Germany Received 11 March 2010; received in revised form 30 May 2010; accepted 30 May 2010 Available online 2 July 2010 Abstract In this paper, the intrinsic complexities of the experimental examination of hydrogen embrittlement are discussed. On the basis of these complexities, an experimental approach, in situ electrochemical nanoindentation, is proposed and performed on different materials. This technique is capable of registering the onset of plasticity in extremely small volumes, namely perfect crystals in hydrogen-free and charged conditions. It is shown that hydrogen reduces the required stress for the onset of plasticity, i.e. homogeneous dislocation nucle- ation by reduction in the shear modulus, dislocation line energy and stacking fault energy. The change in the shear modulus can be related to reduction in crystal cohesion whereas the reduction in dislocation line energy and stacking fault energy are explained by the defactant concept, i.e. reduction in the defect formation energy in the presence of hydrogen. Thus, neither hydrogen-enhanced dec- ohesion nor hydrogen-enhanced plasticity, but the reduction in the cohesion and defect formation energy are responsible for hydrogen embrittlement. 2010 Acta Ma