# Relaxation and Devitrification of Mg66Zn30Ca4 Metallic Glass

## TL;DR

This study explores the thermal and structural behavior of a biodegradable Mg66Zn30Ca4 metallic glass, revealing its crystallization process and potential for medical applications.

## Contribution

The study identifies the crystallization sequence and structural relaxation behavior of Mg66Zn30Ca4 metallic glass using advanced analytical techniques.

## Key findings

- The alloy exhibits a wide supercooled liquid region of 58 K, suitable for thermoplastic forming.
- Crystallization involves the formation of Mg51Zn20, Mg, and Ca8Mg26.1Zn57.9 phases during devitrification.
- The previously reported IM1 phase was not confirmed in this study.

## Abstract

Mg66Zn30Ca4 metallic glass is a promising biodegradable material due to its high strength, corrosion resistance, and excellent glass-forming ability. In this study, we investigated its thermal stability, structural relaxation, and crystallization behavior using high-energy synchrotron-based X-ray diffraction and DSC analysis. The glass exhibits a wide supercooled liquid region of 58 K, allowing for thermoplastic forming. Structural relaxation experiments revealed nearly a complete relaxation in the first cycle below the first crystallization peak. Upon heating, the alloy undergoes a complex, multi-step devitrification involving successive formation of crystalline phases: Mg51Zn20 (orthorhombic), Mg (hexagonal), and a Ca–Mg–Zn intermetallic compound Ca8Mg26.1Zn57.9, denoted as IM3. Phase identification was carried out by Rietveld refinement, and the evolution of lattice parameters demonstrated anisotropic thermal expansion, particularly in the Mg51Zn20 phase. Notably, the presence of the IM1 Ca3MgxZn15−x, with the 4.6 ≤ x ≤ 12 phase reported in earlier studies, was not confirmed. This work deepens the understanding of phase stability and crystallization mechanisms in Mg-based metallic glasses and supports their future application in biodegradable implants.