Crystallization of metallic glass as a grain-boundary nucleated process: experimental and theoretical evidence for the grain structure of metallic glasses

TL;DR

This paper provides experimental and theoretical evidence that metallic glasses crystallize via grain-boundary nucleation, challenging the view of glasses as homogeneous frozen liquids, and explains complex crystallization behaviors through a simple analytical model.

Contribution

It introduces experimental DSC and Avrami data supporting grain-boundary nucleation in metallic glasses and develops a model explaining observed crystallization patterns.

Findings

Grain boundaries are the nucleation sites in metallic glass crystallization.

Two-peak DSC curves and three-step Avrami plots are explained by boundary nucleation.

The analytical model clarifies conditions leading to complex crystallization behaviors.

Abstract

Experimental DSC and Avrami curves for the crystallization of metallic glasses demonstrate nucleation at grain boundaries and thus indicate their grain structure, which refutes the generally accepted idea of glass as a homogeneous frozen liquid obtained as a result of avoiding crystallization. Under certain conditions, this nucleation mechanism results in the appearance of two-peak DSC curves and three-step Avrami plots which are observed experimentally. To clarify these conditions, isothermal and non-isothermal surface-nucleated crystallization of a spherical particle is considered within the framework of a simple analytical model of nucleation and growth.