Microstructural anisotropy of magnetocaloric gadolinium cylinders : effect on the mechanical properties of the material

Steiner Petrovič, Darja (author), Šturm, Roman (author), Naglič, Iztok (author), Markoli, Boštjan (author), Pepelnjak, Tomaž (author)

The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces.

• Language: English
• Keywords: Gadolinium, magnetocaloric, inclusions, selective oxidation, mechanical properties
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering; NTF - Faculty of Natural Sciences and Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2016
• Number of pages: 14 str.
• Numbering: Vol. 9, iss. 5, art. 382
• PID: 20.500.12556/RUL-131557
• UDC: 620.1:67.017(045)
• ISSN on article: 1996-1944
• DOI: 10.3390/ma9050382
• COBISS.SI-ID: 1206698
• Publication date in RUL: 29.09.2021

Record is a part of a journal

• Title: Materials
• Shortened title: Materials
• Publisher: MDPI
• ISSN: 1996-1944
• COBISS.SI-ID: 33588485

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 17.05.2016

Secondary language

• Language: Slovenian
• Keywords: magnetokaloričnost, gadolinij, vključki, selektivna oksidacija, mehanske lastnosti