Hot Uniaxial Pressing and Pressureless Sintering of AlCrCuFeMnNi Complex Concentrated Alloy-A Comparative Study

• Published in: Materials 2024-11, Vol.17 (22), p.5457
• Main Authors: Silva, Tiago, Simões, Pedro, Lopes, Augusto
• Format: Article
• Language: English
• Subjects: Alloying elements; Alloys; Aluminum oxide; Comparative studies; Electron backscatter diffraction; External pressure; Gettering; Grain size distribution; Hardness tests; Helium; Hot pressing; Hydrogen; Loose powder sintering; Mechanical properties; Mixtures; Oxidation; Oxides; Oxygen; Partial pressure; Particle size; Plasma sintering; Powder metallurgy; Powders; Pressing; Sensors; Sintering; Specialty metals industry; Specific gravity; Temperature; X-ray spectroscopy
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17225457

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 °C for 1 h with an applied pressure of 30 MPa and by PLS at 1050 °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.