abstract
External pressure is often applied during sintering to obtain materials with improved properties. For complex concentrated alloys (CCAs), this processing step is commonly performed in vacuum. However, this can promote the evaporation of elements and increase the oxide content, thereby degrading the properties of the alloy. In this study, we compared the microstructures and properties of AlCrCuFeMnNi CCA samples obtained by hot uniaxial pressing sintering (HPS) and pressureless sintering (PLS) using a helium atmosphere purified by an oxygen getter system. The powders were prepared from mixtures of CrFeMn, AlNi and Cu and sintered by HPS at 900 degrees C for 1 h with an applied pressure of 30 MPa and by PLS at 1050 degrees C for 1 h. The samples were characterised using X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattering diffraction, density measurements and hardness tests. It was found that the oxygen getter system promoted oxygen partial pressure values at sintering temperatures similar to those of a mixture of 90% helium and 10% hydrogen. The HPS allowed us to obtain almost fully dense samples with a smaller average grain size and finer distribution of aluminium oxides than PLS. These differences increased the hardness of the samples sintered under pressure.
keywords
HIGH-ENTROPY ALLOYS; MECHANICAL-PROPERTIES; TENSILE PROPERTIES; MICROSTRUCTURE; ATMOSPHERE
subject category
Chemistry; Materials Science; Metallurgy & Metallurgical Engineering; Physics
authors
Silva, T; Simoes, P; Lopes, A
our authors
Augusto Luís Barros Lopes
Assistant Professor
Tiago Filipe Vieira da Silva
PhD StudentProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
This work was developed within the scope of the following projects: 1-PRR-Plano de Recuperacao e Resiliencia and the NextGenerationEU funds at Universidade de Aveiro,through the scope of the Agenda for Business Innovation "Ecoceramica e Cristalaria de Portugal"(Project no. 76 with the application C644916391-00000029). 2-CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC). 3-HiTClean-Fornos limpos de alta temperatura para novas tecnologias defabrico aditivo e ligas de alta entropia", com o Numero 39736, com o apoio financeiro proveniente do Fundo Europeu de Desenvolvimento Regional-FEDER, atraves do POCI.