Ultrafast spherulitic crystal growth as a stress-induced phenomenon specific of fragile glass-formers

TL;DR

This paper presents a model explaining the ultra-fast spherulitic crystal growth near the glass transition as a stress-induced phenomenon in fragile glass-formers, highlighting the role of stress dynamics and structural features.

Contribution

It introduces a novel stress-based model for fast crystal growth in fragile glass-formers, emphasizing the importance of stress generation, release, and spherulitic sub-structure.

Findings

Fast growth occurs close to the glass transition.

High fragility and spherulitic sub-structure are essential for fast growth.

The transition is hysteretic, testable experimentally.

Abstract

We propose a model for the abrupt emergence, below temperatures close to the glass transition, of the ultra-fast (GC) steady mode of spherulitic crystal growth in deeply undercooled liquids. We interpret this phenomenon as controlled by the interplay between the generation of stresses by crystallization and their partial release by flow in the surrounding amorphous visco-elastic matrix. Our model is consistent with both the observed ratios ($\sim10^4$) of fast-to-slow velocities and the fact that fast growth emerges close to the glass transition. It leads us to conclude that the existence of a fast growth regime requires both (i) a high fragility of the glassformer; (ii) the fine sub-structure specific of spherulites. It finally predicts that the transition is hysteretic, thus allowing for an independent experimental test.