Study of the Martensitic Transformation in a Magnetocaloric MnNiFeCoSiGe High-Entropy Alloy

• Grant number: 25/02882-8
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: June 30, 2027
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Francisco Gil Coury
• Grantee: Pedro Henrique de Siqueira Mancilha
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 22/02770-7 - Integrated Computational Materials Engineering ICME: applied to modeling, production, characterization and testing high entropy alloys, AP.PNGP.PI

Abstract

Due to the large number of possible compositions, medium- and high-entropy alloys exhibit a broad spectrum of mechanical and functional properties when compared to traditional alloys, including magnetocaloric properties. The first magnetocaloric high-entropy alloys contained rare-earth elements in their composition, but recently, alloys without these elements have been developed. The MnNiFeCoSiGe system, in particular, has several compositions of the type (MnNiFeCo)2(SiGe)1 that exhibit a strong magnetocaloric effect due to a magnetostructural transformation in which a hexagonal austenitic and paramagnetic phase transforms into an orthorhombic martensitic and ferromagnetic phase upon cooling. Some alloys from this system are promising for application in magnetic refrigeration systems, as they present a combination of strong magnetocaloric effect, low thermal hysteresis, and low Curie temperature, such as the composition Mn0.6Ni0.6Fe0.4Co0.4Si0.64Ge0.36. Although the martensitic transformation exhibited by the alloys in this system is behind the strong magnetocaloric effect they possess, the transformation mechanism is still not well understood, but it is crucial to better comprehend it in order to determine the true potential of these alloys. Thus, this project aims to study in detail the martensitic transformation mechanism in the Mn0.6Ni0.6Fe0.4Co0.4Si0.64Ge0.36 alloy, chosen for its excellent combination of properties. The results of this study will contribute to a deeper understanding of the mechanisms of martensitic transformation in magnetocaloric high-entropy alloys, enabling advances toward the application of these alloys in efficient and sustainable magnetic refrigeration systems.