Lattice distortion and atomic displacements during the fcc/bcc martensitic transformation

TL;DR

This paper models atomic displacements and lattice distortions during the fcc to bcc martensitic transformation, highlighting the role of angular distortion as an order parameter and proposing an alternative to classical theories.

Contribution

It introduces a new approach to modeling martensitic transformation that emphasizes lattice distortion and atomic displacements, challenging traditional shear-based theories.

Findings

The distortion for Kurdjumov-Sachs respects dense direction and plane parallelism.

The model aligns with various orientation relationships like Bain, Pitsch, and KS.

Angular distortion serves as a natural order parameter for the transition.

Abstract

From our previous models of martensitic transformation, the continuous matrices of atomic displacements and lattice deformations from face-centred-cubic (fcc) to body centred-cubic (bcc) phases are calculated in agreement with different possible final orientation relationships, such as Bain, Pitsch and Kurdjumov-Sachs (KS). The angular distortion introduced in the calculations appears a natural order parameter of transition. The distortion corresponding to KS is the only one that respects the parallelism of a dense direction and of a dense plane of both the fcc and bcc phases. This paper gives an alternative to the classical crystallographic theories and shear concepts associated to martensitic transformations.