Orientational Equidistance Method for Solving Orientation Relationship From Product Variants: Application to Steel

Abstract

A three-step procedure has been evolved for finding the orientation relationship (OR) between parent austenite and product ferrite phase, from the room temperature microtexture data of ferritic/martensitic steel. In the first step, the frequently occurring misorientations between product ferrite variants are sought from the electron backscatter diffraction (EBSD) dataset. This is carried out by calculating the ‘misorientation angle-rotation axis’ values across all neighboring pair of ferrite pixels, and plotting them in a parametric space to detect the prominent misorientation peaks. Identification of ‘concurrent relative orientation’ of product variants, i.e., the second step, is resolved by comparing the observed misorientation peak positions with the inter-variant relation set of Kurdjumov–Sachs (KS) OR. The final crucial step of solving the OR based on the ‘Orientational Equidistance’ principle of parent phase from all its product phase variants is implemented in the Rodrigues–Frank parametric space. The procedure is illustrated using an large area EBSD dataset of normalized and tempered 9Cr–1Mo–0.1C steel, and the optimum orientation relation is determined to be ~44.0°[0.151 0.137 0.979], which is 2.4° deviated from KS OR.