The morphology of lath martensite: a new perspective

TL;DR

This paper introduces a mathematical model to predict the morphology of (5 5 7) lath martensite in low-carbon steels, emphasizing energy minimization and compatibility, revealing a microstructure similar to plate martensite with twinning mechanisms.

Contribution

It presents a novel theoretical framework for predicting lath martensite features based on energy considerations and deformation compatibility.

Findings

Predicts (5 5 7) habit planes via energy minimization.

Identifies a deformation mechanism with minimal atomic movement.

Microstructure resembles plate martensite with twinning.

Abstract

A mathematical framework is proposed to predict the features of the (5 5 7) lath transformation in low-carbon steels based on energy minimisation. This theory generates a one-parameter family of possible habit planes and a selection mechanism then identifies the (5 5 7) normals as those arising from a deformation with small atomic movement and maximal compatibility. While the calculations bear some resemblance to those of double shear theories, the assumptions and conclusions are different. Interestingly, the predicted microstructure morphology resembles that of plate martensite, in the sense that a type of twinning mechanism is involved.