Crystallography of [0 1 1]/54.7° lath boundary and cementite in tempered 0.2C steel

The crystallographic structures of the [0 1 1]/54.7° lath boundary and the intralath and interlath cementite precipitates in a 0.2C steel tempered at 400 °C have been observed by high resolution transmission electron microscopy and discussed in terms of the O-lattice model. The [0 1 1]/54.7° lath boundary which is composed of one Kurdjumov-Sachs variant ((alpha)1) and one Nishiyama–Wasserman variant ((alpha)2) is likely to facet on the (0 12 7)(alpha)1//(5 19 14)(alpha)2 irrational plane. The O-lattice analysis indicated that the facet coincides with a plane with a high density of O-points. Intralath cementite obeys the Isaichev orientation relationship (OR) with ferrite and has a habit plane of (1 0 1)(theta)//(1 2 1)(alpha). Interlath cementite precipitating on the [0 1 1]/54.7° boundary maintains a strict Bagaryatskii OR with the ferrite on one side of the boundary and has a (1 0 0)(theta) habit plane.