The role of microstructure in fatigue crack initiation of 9–12%Cr reduced activation ferritic–martensitic steel. (March 2015)

• Record Type: Journal Article
• Authors: Batista, M.N.; Marinelli, M.C.; Hereñú, S.; Alvarez-Armas, I.
• Is Part Of: International journal of fatigue. Volume 72(2015)
• Page Start: 75
• Page End: 79
• Publication Date: 2015-03
• Subjects: Ferritic–martensitic steel -- LCF -- Microstructure -- Microcrack nucleation -- EBSD technique; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2014.11.006
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: As-received: small-highly misoriented areas and large-slightly misoriented areas. After cycling: extrusions over large areas of slightly misoriented lath structures. We observed pile-ups of dislocation stress concentration. The observed pile-ups speak of the irreversibility of slip during cycling straining. Dislocation arrangement is the origin of microcrack nucleation at lath boundaries. Abstract: Electron back-scattered diffraction together with scanning and transmission electron microscopy were used to study nucleation of microstructural fatigue cracks in reduced-activation ferritic–martensitic steel, EUROFER 97. Cylindrical specimens were cycled over different plastic-strain ranges in order to evaluate the evolution of the dislocation structure. Surface-damage evolution was studied in smooth notched specimens by an optical in situ system equipped with a high-resolution camera. In order to understand the crack-initiation mechanism, the dislocation microstructure that develops in the near-surface regions of the notch was compared with that of the bulk. The results demonstrate a strong influence of lath-martensite boundaries on fatigue-crack nucleation.