Estimation of martensite feature size in a low-carbon alloy steel by microtexture analysis of boundaries. (January 2015)

• Record Type: Journal Article
• Authors: Karthikeyan, T.; Dash, Manmath Kumar; Saroja, S.; Vijayalakshmi, M.
• Is Part Of: Micron. Volume 68(2015:Jan.)
• Page Start: 77
• Page End: 90
• Publication Date: 2015-01
• Subjects: Steels -- Orientation relationship -- Martensite boundaries -- Microtexture analysis -- EBSD; Microscopy -- Periodicals; Electron Probe Microanalysis -- Periodicals; Microscopy -- Periodicals; Microscopie -- Périodiques; Microscopy; Periodicals; 502.82
• DOI: 10.1016/j.micron.2014.09.008
• Languages: English
• ISSNs: 0968-4328

Abstract

Highlights: EBSD data is used to identify hierarchical features of martensite in 9Cr–1Mo steel. Misorientation angle-axis analysis provides classification of boundary structures. Quaternion algebra is far superior in carrying out the misorientation calculations. Enhancement factor concept is used to identify the deviation from OR. Martensite boundary maps are arrived at and used to determine the feature size. Abstract: A methodology for classifying the hierarchy of martensite boundaries from the EBSD microtexture data of low-carbon steel is presented. Quaternion algebra has been used to calculate the ideal misorientation between product α variants for Kurdjumov–Sachs (KS) and its nearby orientation relationships, and arrive at the misorientation angle-axis set corresponding to packet (12 types), block (3 types) and sub-block boundaries. Analysis of proximity of experimental misorientation between data points from the theoretical misorientation set is found to be useful for identifying the different types of martensite boundaries. The optimal OR in the alloy system and the critical deviation threshold for identification of martensite boundaries could both be ascertained by invoking the 'Enhancement Factor' concept. The prior-γ grain boundaries, packet, block and sub-block boundaries could be identified reasonably well, and their average intercept lengths in a typical tempered martensite microstructure of 9Cr–1Mo–0.1C steel was estimated as 31 μm, 14 μm, 9 μm and 4 μm respectively.