Disorder-Driven Pretransitional Tweed in Martensitic Transformations

TL;DR

This paper investigates the origin of tweed patterns in martensitic transformations, revealing that compositional disorder and lattice constraints induce a frustrated, glassy phase, supported by simulations and experimental comparisons.

Contribution

The study introduces a two-dimensional model explaining tweed formation as a disorder-induced glassy phase, aligning well with experimental diffraction data.

Findings

Tweed patterns result from compositional disorder and lattice frustration.

Numerical simulations reproduce experimental diffraction patterns.

The model outperforms alternative strain-disorder coupling models.

Abstract

Defying the conventional wisdom regarding first--order transitions, {\it solid--solid displacive transformations} are often accompanied by pronounced pretransitional phenomena. Generally, these phenomena are indicative of some mesoscopic lattice deformation that ``anticipates'' the upcoming phase transition. Among these precursive effects is the observation of the so-called ``tweed'' pattern in transmission electron microscopy in a wide variety of materials. We have investigated the tweed deformation in a two dimensional model system, and found that it arises because the compositional disorder intrinsic to any alloy conspires with the natural geometric constraints of the lattice to produce a frustrated, glassy phase. The predicted phase diagram and glassy behavior have been verified by numerical simulations, and diffraction patterns of simulated systems are found to compare well with experimental data. Analytically comparing to alternative models of strain-disorder coupling, we show that the present model best accounts for experimental observations.