Partial Equilibration Scenario in 3D athermal martensites quenched below first-order transition temperatures

TL;DR

This study uses Monte Carlo simulations to test the Partial Equilibration Scenario in 3D athermal martensites, revealing how entropy barriers and effective temperatures influence phase transformation delays below transition temperatures.

Contribution

It provides the first detailed simulation validation of the PES in 3D martensitic transitions, highlighting the role of effective temperature and entropy barriers in phase conversion delays.

Findings

Exponential-tail distribution of heat releases confirms PES predictions.

Effective temperature vanishes linearly near a critical temperature, indicating barrier divergence.

Martensitic delays follow Vogel-Fulcher-Tammann-like divergence patterns.

Abstract

To test a Partial Equilibration Scenario (PES) of Ritort and colleagues, we do Monte Carlo simulations of discretized-strain spin models, for four 3D martensitic structural transitions under quenches to a bath temperature $T <T_0$ below a first-order transition. The ageing system faces entropy barriers, in {\it searches} for energy-lowering passages between quasi-microcanonical energy shells. We confirm the PES signature of an exponential-tail distribution of intermittent heat releases to the bath, scaled in an effective temperature, that in our case, depends on the quench. When its inverse $\beta_{eff} (T) \equiv 1/T_{eff} (T) $ vanishes below a `martensite start' temperature $T_1$ of avalanche conversions, then entropy barriers vanish. When this search temperature $T_{eff} (T)$ vanishes, PES cooling is arrested, as entropy barriers diverge. We find a {\it linear} vanishing of $T_{eff}(T)\sim T_d -T$, below a delay-divergence temperature $T_d$ in between, $T_1 < T_d < T_0$. Martensitic conversion delays $e^{1/T_{eff}} \sim e^{1/(T_d -T)}$ thus have Vogel-Fulcher-Tammann like divergences. Post-quench delay data extracted from simulations and athermal martensitic alloys, are both consistent with predictions.