Oxygen effect in high entropy refractory alloys

• Grant number: 20/04444-4
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): July 01, 2020
• Effective date (End): February 29, 2024
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal researcher: Marcelo Falcão de Oliveira
• Grantee: Carolina Soares
• Home Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The growing need for high temperature resistant metal alloys has promoted the development of new materials, including Refractory High Entropy Alloys (RHEAs). Its first compositions were reported in 2010 and its mechanical resistance at high temperature outperformed the traditionally used nickel super alloys. REAHs are metallic alloys composed of 5 or more elements, most of them refractory, with content between 5 and 35% (at.) and which have an entropy of a mixture sufficiently high to stabilize the formation of a solid solution in detriment of the formation of intermetallics. One of the first challenges for using RHEAs is the production of well-defined geometry parts, such as plates or cylinders. Since its production is carried out by electric arc casting, however in these cases it is not possible to inject it into a mold. Being alternative produce then by powder metallurgy. In addition, because they are composed of elements that are very reactive with oxygen, such as Ti and Zr, contamination is common. However, the effect of oxygen is still poorly studied and there is no consensus regarding its effect on the ductility of these alloys. There are studies that claim that its presence in a solid solution can increase ductility, while others claim that such element is harmful. Therefore, this project aims to test in a systematic and controlled way the influence of oxygen on the microstructure and mechanical properties, at room temperature and high temperature, of RHEAs produced by metallurgy of pre-alloyed powder, produced by hydrogenation, and then sintered. (AU)