Influence of Aluminum on Short-Range Chemical Ordering, Mechanical Properties, and Oxidation Resistance of NbTaTi High-Entropy Alloys

• Grant number: 25/01475-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2025
• End date: September 30, 2028
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Francisco Gil Coury
• Grantee: Isabela Dainezi
• 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

High-Entropy Alloys (HEAs) have emerged as a promising class of materials due to their exceptional mechanical properties and resistance to harsh environments. Among them, NbTaTi-based HEAs stand out for their potential applications in high-temperature and structural components. However, key aspects such as the influence of Short-Range Ordering (SRO) on mechanical properties and the oxidation behavior of these alloys remain poorly understood. This study investigates two parallel aspects: (i) the role of aluminum (Al) in inducing and modifying SRO in NbTaTi-based HEAs and its impact on mechanical behavior, and (ii) the oxidation resistance of these alloys, with a particular focus on the effect of Al additions. To achieve these objectives, NbTaTi and (NbTaTi)95Al5 alloys will be fabricated and subjected to thermomechanical treatments to induce different degrees of SRO. Mechanical tests at various strain rates and temperatures will be conducted to assess the effect of SRO on deformation mechanisms and yield strength. In parallel, oxidation resistance will be evaluated through high-temperature exposure in controlled environments, analyzing the formation and stability of protective oxide scales. Advanced characterization techniques, including Scanning Electron Microscopy (SEM), Electron Back-Scattered Diffraction (EBSD), X-Ray Diffraction (XRD), and Differential Scanning Calorimetry (DSC), will be employed to investigate microstructure and ordering phenomena. The findings of this research will contribute to a deeper understanding of SRO formation in refractory HEAs and its influence on mechanical properties while also providing insights into the oxidation behavior of NbTaTi-based alloys. (AU)