On the Mechanism of Martensite Formation during Short Fatigue Crack Propagation in Austenitic Stainless Steel:Experimental Identification and Modelling Concept
During fatigue of metastable austenitic steels,local plasticity is linked with the formation of martensite.It was shown that cubic a martensite nucleates at slip band and 8 martensite intersection sites ahead of growing fatigue cracks.Since such intersections require the operation of alternate slip systems,martensite formation was found only for shear-controlled single-slip crack propagation (mode iD prevailing during the early propagation phase of microstructurally short fatigue cracks.Surprisingly,cracks were found not to initiate within martensitically transformed grains but by a fraction of 70% along twin boundaries.The extent of martensite formation ahead of a propagating crack increases with increasing crack length and eventually,gives rise to transformation-induced crack-closure effects.The interaction between the crack tip plasticity and the local microstructure was quantitatively analysed by automated electron back-scatter diffraction (EBSD) in the scanning electron microscope (SEM) applied to the electro-polished surfaces of fatigue specimens.Following a geometrical model for martensitic transformation,further analysis of the relevant fatigue mechanism became possible aiming to both mechanism-based life prediction and tailoring fatigue resistant microstructures.
austenitic steels martensitic transformation fatigue crack propagation short crack model
Ulrich Krupp Ingmar Roth Hans-Jürgen Christ Martin Kübbeler Claus-Peter Fritzen
Faculty of Engineering and Computer Science,University of Applied Sciences Osnabrück,49009 Osnabrück Science and Technology,University of Siegen,57068 Siegen,Germany
国际会议
北京
英文
1-9
2013-06-16（万方平台首次上网日期，不代表论文的发表时间）