Crystallographic Analysis of Transformation Behavior of Acicular Ferrite from B1-type Compounds in Steels

Abstract

Crystallographic analysis was carried out on acicular ferrites (AFs) of steel that nucleated on B1-type compounds embedded in steels during the isothermal transformation from austenite (γ) to ferrite (α), and the orientation relationship between α, γ, and the compounds and the AF formation behavior were correlated by varying the B1-type compound, steel, and transformation temperature. The results demonstrated that all the AFs satisfy the Kurdjumov–Sachs orientation relationship with the prior γ, and in addition, some of the AFs have specific low-index orientation relationships with the B1-type compounds and nucleate earlier than others. Among the specific low-index orientation relationships, furthermore, AFs satisfying the Baker–Nutting orientation relationship, which gives the lowest interfacial energy between α and a compound, nucleate preferentially.