Thermomechanical Treatments for Modifying the As Cast Microstructure of High Entropy Alloys of the TiVNbCrMn System

• Grant number: 23/09426-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2023
• End date: June 30, 2024
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Kátia Regina Cardoso
• Grantee: Larissa Nunes Hirata
• Host Institution: Instituto de Ciência e Tecnologia (ICT). Universidade Federal de São Paulo (UNIFESP). Campus São José dos Campos. São José dos Campos , SP, Brazil

Abstract

In the last two decades, there has been a growing scientific and technological interest in high entropy alloys (HEA), mainly due the vast number of possible compositions achievable within this novel alloy concept, offering possibilities for tailoring compositions, microstructures, and properties for different structural and functional applications. One potential application of HEA is their use as solid-state hydrogen storage materials by forming metallic hydrides. The research group behind this project has been investigating alloys from the TiVNbCrMn system for this purpose, aiming to obtain single-phase alloys with a body-centered cubic structure (BCC), suitable for the absorption of hydrogen. These alloys have been produced using the electric arc melting technique and have been characterized in their as-cast state. In this state, the alloys exhibit dendritic morphology, large grains and segregation of alloying elements in the interdendritic regions, which may impact mechanical and functional properties. Heat treatments and/or thermomechanical processing can be employed to modify the as-cast microstructure, enhancing alloys' homogeneity, and inducing microstructural changes such as grain refinement, which is particularly important in alloys for hydrogen storage as it increases the surface area and grain boundary density, thereby favoring diffusion and hydrogen absorption/desorption processes. This project aims to produce TiVNbCrMn HEA through electric arc melting and evaluate the effect of thermomechanical treatments on the alloys' microstructure. The alloy samples will be subjected to homogenization heat treatments and thermomechanical processing through hot open-die forging. The alloys will be structurally and microstructurally characterized by X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. The results obtained should contribute to a better understanding of the correlations between processing and final structure of HEA for their potential application in hydrogen storage.