Re-equilibration after quenches in athermal martensites:Conversion-delays for vapour to liquid domain-wall phases

TL;DR

This paper investigates the nonequilibrium dynamics of martensitic transformations after quenches, revealing how entropy barriers cause delays and stress-dependent re-equilibration in athermal systems.

Contribution

It identifies the entropy barrier in Fourier space as the cause of delay times and introduces a stress-dependent effective temperature concept for re-equilibration.

Findings

Delay times arise from entropy barriers in Fourier space.

Strain structure factors facilitate rare pathway searches.

Effective temperature re-equilibrates to the bath temperature.

Abstract

Entropy barriers and ageing states appear in martensitic structural-transition models, slowly re-equilibrating after temperature quenches, under Monte Carlo dynamics. Concepts from protein folding and ageing harmonic oscillators turn out to be useful in understanding these nonequilibrium evolutions. We show how the athermal, non-activated delay time for seeded parent-phase austenite to convert to product-phase martensite, arises from an identified entropy barrier in Fourier space. In an ageing state of low Monte Carlo acceptances, the strain structure factor makes constant-energy searches for rare pathways, to enter a Brillouin zone `golf hole' enclosing negative energy states, and to suddenly release entropically trapped stresses. In this context, a stress-dependent effective temperature can be defined, that re-equilibrates to the quenched bath temperature.