Spatial variation of short-range order in amorphous intergranular complexions

TL;DR

This study investigates the spatial variation of short-range order in amorphous intergranular complexions, revealing how these structures differ from bulk amorphous materials and depend on temperature and interface orientation.

Contribution

It introduces a Voronoi tessellation method to analyze short-range order in amorphous complexions and identifies distinct regions and their temperature-dependent behaviors.

Findings

Amorphous complexions have three distinct regions with varying short-range order.

Transition region thickness depends on film thickness at low temperatures.

Short-range order varies with interface plane at low temperatures but not at high temperatures.

Abstract

Amorphous materials lack long-range order but short-range order can still persist through the recurrence of similar local packing motifs. While the short-range order in bulk amorphous phases has been well studied and identified as an intrinsic factor determining the material properties, these features have not been studied in disordered intergranular complexions. In this work, the short-range order in two types of amorphous complexions is studied with a Voronoi tessellation method. Amorphous complexions can have three distinct regions: amorphous-crystalline interfaces, regions deep inside the films that have short-range order identical to a bulk amorphous phase, and transition regions that connect the first two regions. However, thin amorphous films contain only the amorphous-crystalline interface and the transition region, providing further evidence of the constraints imposed by the abutting crystals. The thickness of the transition region depends on film thickness at low temperatures but becomes thickness-independent at high temperatures. Similarly, the complexion short-range order is dependent on the interfacing crystal plane at low temperatures, but this effect is lost at high temperatures. Our findings show that amorphous complexions contain spatial gradients in short-range order, meaning they are both structurally and chemically different from bulk metallic glasses.