Three-dimensional Quantitative Evaluation of the Lamellar Curvature in Pearlitic Steel Based on an Orientation Analysis of Cementite

To quantitatively evaluate the three-dimensional lamellar curvature in pearlitic steel, the crystallographic orientation rotation of ferrite and cementite was analyzed using scanning electron microscopy and electron backscattering diffraction. In the hypereutectoid steel containing 0.92% C, 0.30% Mn, 0.20% Si, and 0.19% Cr, the ferrite-cementite interfaces in some colonies were confirmed to match well with those having frequently observed habit planes with the Pitsch-Petch orientation relationship. It was also confirmed that the ferrite and cementite near the ferrite-cementite interface rotated toward the same orientation to maintain the Pitsch-Petch orientation relationship and the habit plane. Based on the confirmation that the ferrite-cementite interface is well approximated by (010) plane of the adjacent cementite, the lamellae were revealed to have three-dimensional anisotropic curvature.