Analysis of the Crystallization Kinetics and Thermal Stability of the Amorphous Mg72Zn24Ca4 Alloy.

Bartosz Opitek,Michał Szucki,Łukasz Rogal,Grzegorz Piwowarski,Janusz Lelito,Łukasz Gondek

doi:10.3390/ma14133583

Abstract

The aim of this study was to analyze the crystallization of the Mg72Zn24Ca4 metallic glass alloy. The crystallization process of metallic glass Mg72Zn24Ca4 was investigated by means of the differential scanning calorimetry. The glass-forming ability and crystallization are both strongly dependent on the heating rate. The crystallization kinetics, during the isothermal annealing, were modelled by the Johnson–Mehl–Avrami equation. Avrami exponents were from 2.7 to 3.51, which indicates diffusion-controlled grain growth. Local exponents of the Johnson–Mehl–Avrami equation were also calculated. In addition, the Mg phase—being the isothermal crystallization product—was found, and the diagram of the time–temperature phase transformation was developed. This diagram enables the reading of the start and end times of the crystallization process, occurring in amorphous ribbons of the Mg72Zn24Ca4 alloy on the isothermal annealing temperature. The research showed high stability of the amorphous structure of Mg72Zn24Ca4 alloy at human body temperature.

Highlights

There have been recent investigations of various materials used in orthopedics [1,2,3]
Against this backdrop of mounting health hazards caused by nickel toxicity, nickel-free nitrogen containing austenitic stainless steels with lower toxicity to the human body are thought to be developed as the generation of metallic implant materials
The X-ray diffraction (XRD) investigations of ribbons indicated the amorphous structure of the Mg72Zn24Ca4 alloy with a small amount of the crystalline Mg1−xZnx phase

Summary

Introduction

There have been recent investigations of various materials used in orthopedics [1,2,3]. The maximum rate of nickel release, due to corrosion in patients who have implants made of nickel alloys, is estimated as 20 mg kg−1 day−1 [14] Against this backdrop of mounting health hazards caused by nickel toxicity, nickel-free nitrogen containing austenitic stainless steels with lower toxicity to the human body are thought to be developed as the generation of metallic implant materials. It should be mentioned here that materials with a mixed (amorphous-crystalline) structure may still have good plastic properties and anticorrosion resistance [26] This is what makes understanding the crystallization kinetics of Mg-based metallic glasses so important. This is due to the fact that the process requires a slower cooling rate for an alloy with a eutectic or approximately eutectic composition than for a hypoeutectic alloy

Materials and Experimental Methods

Results and Discussion

Conclusions