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Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K
This paper presents tests of metallic glass based on Mg(72)Zn(24)Ca(4) alloy. Metallic glass was made using induction melting and further injection on a rotating copper wheel. A differential scanning calorimeter (DSC) was used to investigate the phase transformation of an amorphous ribbon. The tests...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2020
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345161/ https://www.ncbi.nlm.nih.gov/pubmed/32585843 http://dx.doi.org/10.3390/ma13122815 |
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author | Lelito, Janusz |
author_facet | Lelito, Janusz |
author_sort | Lelito, Janusz |
collection | PubMed |
description | This paper presents tests of metallic glass based on Mg(72)Zn(24)Ca(4) alloy. Metallic glass was made using induction melting and further injection on a rotating copper wheel. A differential scanning calorimeter (DSC) was used to investigate the phase transformation of an amorphous ribbon. The tests were carried out at an isothermal annealing temperature of 507 K. The Kolmogorov-Johnson-Mahl-Avrami-Evans model was used to analyze the crystallization kinetics of the amorphous Mg(72)Zn(24)Ca(4) alloy. In this model, both Avrami’s exponent n and transformation rate constant K were analyzed. Both of these kinetic parameters were examined as a function of time and the solid fraction. The Avrami exponent n value at the beginning of the crystallization process has value n = 1.9 and at the end of the crystallization process has value n = 3.6. The kinetic constant K values change in the opposite way as the exponent n. At the beginning of the crystallization process the constant K has value K = 9.19 × 10(−7) s(−n) (ln(K) = −13.9) and at the end of the crystallization process has the value K = 6.19 × 10(−9) s(−n) (ln(K) = −18.9). These parameters behave similarly, analyzing them as a function of the duration of the isothermal transformation. The exponent n increases and the constant K decreases with the duration of the crystallization process. With such a change of the Avrami exponent n and the transformation rate constant K, the crystallization process is controlled by the 3D growth on predetermined nuclei. Because each metallic glass has a place for heterogeneous nucleation, so called pre-existing nuclei, in which nucleation is strengthened and the energy barrier is lowered. These nuclei along with possible surface-induced crystallization, lead to rapid nucleation at the beginning of the process, and therefore a larger transformed fraction than expected for purely uniform nucleation. These sites are used and saturated with time, followed mainly by homogeneous nucleation. In addition, such a high value of the Avrami exponent n at the end of the crystallization process can cause the impingement effect, heterogeneous distribution of nuclei and the diffusion-controlled grain growth in the Mg(72)Zn(24)Ca(4) metallic glassy alloy. |
format | Online Article Text |
id | pubmed-7345161 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-73451612020-07-09 Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K Lelito, Janusz Materials (Basel) Article This paper presents tests of metallic glass based on Mg(72)Zn(24)Ca(4) alloy. Metallic glass was made using induction melting and further injection on a rotating copper wheel. A differential scanning calorimeter (DSC) was used to investigate the phase transformation of an amorphous ribbon. The tests were carried out at an isothermal annealing temperature of 507 K. The Kolmogorov-Johnson-Mahl-Avrami-Evans model was used to analyze the crystallization kinetics of the amorphous Mg(72)Zn(24)Ca(4) alloy. In this model, both Avrami’s exponent n and transformation rate constant K were analyzed. Both of these kinetic parameters were examined as a function of time and the solid fraction. The Avrami exponent n value at the beginning of the crystallization process has value n = 1.9 and at the end of the crystallization process has value n = 3.6. The kinetic constant K values change in the opposite way as the exponent n. At the beginning of the crystallization process the constant K has value K = 9.19 × 10(−7) s(−n) (ln(K) = −13.9) and at the end of the crystallization process has the value K = 6.19 × 10(−9) s(−n) (ln(K) = −18.9). These parameters behave similarly, analyzing them as a function of the duration of the isothermal transformation. The exponent n increases and the constant K decreases with the duration of the crystallization process. With such a change of the Avrami exponent n and the transformation rate constant K, the crystallization process is controlled by the 3D growth on predetermined nuclei. Because each metallic glass has a place for heterogeneous nucleation, so called pre-existing nuclei, in which nucleation is strengthened and the energy barrier is lowered. These nuclei along with possible surface-induced crystallization, lead to rapid nucleation at the beginning of the process, and therefore a larger transformed fraction than expected for purely uniform nucleation. These sites are used and saturated with time, followed mainly by homogeneous nucleation. In addition, such a high value of the Avrami exponent n at the end of the crystallization process can cause the impingement effect, heterogeneous distribution of nuclei and the diffusion-controlled grain growth in the Mg(72)Zn(24)Ca(4) metallic glassy alloy. MDPI 2020-06-23 /pmc/articles/PMC7345161/ /pubmed/32585843 http://dx.doi.org/10.3390/ma13122815 Text en © 2020 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Lelito, Janusz Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K |
title | Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K |
title_full | Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K |
title_fullStr | Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K |
title_full_unstemmed | Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K |
title_short | Crystallization Kinetics Analysis of the Amorphouse Mg(72)Zn(24)Ca(4) Alloy at the Isothermal Annealing Temperature of 507 K |
title_sort | crystallization kinetics analysis of the amorphouse mg(72)zn(24)ca(4) alloy at the isothermal annealing temperature of 507 k |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345161/ https://www.ncbi.nlm.nih.gov/pubmed/32585843 http://dx.doi.org/10.3390/ma13122815 |
work_keys_str_mv | AT lelitojanusz crystallizationkineticsanalysisoftheamorphousemg72zn24ca4alloyattheisothermalannealingtemperatureof507k |