{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,14]],"date-time":"2026-01-14T16:27:33Z","timestamp":1768408053060,"version":"3.49.0"},"reference-count":46,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2024,11,8]],"date-time":"2024-11-08T00:00:00Z","timestamp":1731024000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>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 \u00b0C for 1 h with an applied pressure of 30 MPa and by PLS at 1050 \u00b0C 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.<\/jats:p>","DOI":"10.3390\/ma17225457","type":"journal-article","created":{"date-parts":[[2024,11,8]],"date-time":"2024-11-08T06:05:41Z","timestamp":1731045941000},"page":"5457","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Hot Uniaxial Pressing and Pressureless Sintering of AlCrCuFeMnNi Complex Concentrated Alloy\u2014A Comparative Study"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3980-8392","authenticated-orcid":false,"given":"Tiago","family":"Silva","sequence":"first","affiliation":[{"name":"Department of Materials and Ceramic Engineering, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"Pedro","family":"Sim\u00f5es","sequence":"additional","affiliation":[{"name":"Termolab\u2014High Temperature Technology, 3750-309 \u00c1gueda, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8594-1779","authenticated-orcid":false,"given":"Augusto","family":"Lopes","sequence":"additional","affiliation":[{"name":"Department of Materials and Ceramic Engineering, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,11,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Gao, M.C., Yeh, J.W., Liaw, P.K., and Zhang, Y. (2016). High-Entropy Alloys Fundamentals and Applications, Springer.","DOI":"10.1007\/978-3-319-27013-5"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"448","DOI":"10.1016\/j.actamat.2016.08.081","article-title":"A critical review of high entropy alloys and related concepts","volume":"122","author":"Miracle","year":"2017","journal-title":"Acta Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/j.actamat.2017.06.027","article-title":"Mapping the world of complex concentrated alloys","volume":"135","author":"Gorsse","year":"2017","journal-title":"Acta Mater."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"721","DOI":"10.1016\/j.crhy.2018.09.004","article-title":"From high-entropy alloys to complex concentrated alloys","volume":"19","author":"Gorsse","year":"2018","journal-title":"C. R. Phys."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"195101","DOI":"10.1063\/1.5051514","article-title":"Rare-earth high entropy alloys with hexagonal close-packed structure","volume":"124","author":"Qiao","year":"2018","journal-title":"J. Appl. Phys."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1468","DOI":"10.1007\/s11661-014-2523-7","article-title":"The mechanical and corrosion behaviors of as-cast and re-melted AlCrCuFeMnNi multi-component high-entropy alloy","volume":"46","author":"Soare","year":"2015","journal-title":"Metall. Mater. Trans."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"142495","DOI":"10.1016\/j.msea.2021.142495","article-title":"Effect of Al content on microstructure and mechanical properties of As-cast AlxFeMnNiCrCu0.5 high-entropy alloys","volume":"832","author":"Nguyen","year":"2022","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1600726","DOI":"10.1002\/adem.201600726","article-title":"Microstructure, mechanical properties, and oxidation behavior of AlxCr0.4CuFe0.4MnNi high entropy alloys","volume":"19","author":"Rao","year":"2017","journal-title":"Adv. Eng. Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"5743","DOI":"10.1016\/j.actamat.2013.06.018","article-title":"The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy","volume":"61","author":"Otto","year":"2013","journal-title":"Acta Mater."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"685","DOI":"10.3166\/acsm.31.685-698","article-title":"Effect of the substitution of Co by Mn in Al-Cr-Cu-Fe-Co-Ni high-entropy alloys","volume":"31","author":"Chen","year":"2006","journal-title":"Ann. Chim. Sci. Mater."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1016\/j.actamat.2013.09.037","article-title":"Effects of Al addition on structural evolution and tensile properties of the FeCoNiCrMn high-entropy alloy system","volume":"62","author":"He","year":"2014","journal-title":"Acta Mater."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Sharma, V., Kumar, S., and Mallick, A. (2023). Light weight MnTiAlNiFe high-entropy alloy (LWHEA) fabricated by powder metallurgy process: Mechanical, microstructure, and tribological properties. Mater. Today Proc.","DOI":"10.1016\/j.matpr.2023.04.157"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2431","DOI":"10.1016\/j.jmrt.2022.01.141","article-title":"Mechanically alloyed high entropy alloys: Existing challenges and opportunities","volume":"17","author":"Kumar","year":"2022","journal-title":"J. Mater. Res. Technol."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Silva, T., and Lopes, A. (2024). Microstructural characterization of AlCrCuFeMnNi complex concentrated alloy prepared by pressureless sintering. Materials, 17.","DOI":"10.3390\/ma17102378"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Murty, B.S., Yeh, J.W., and Ranganathan, S. (2014). High-Entropy Alloys, Elsevier Inc.","DOI":"10.1016\/B978-0-12-800251-3.00002-X"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Sharma, N., Alam, S.N., and Ray, B.C. (2019). Fundamentals of Spark Plasma Sintering (SPS): An Ideal Processing Technique for Fabrication of Metal Matrix Nanocomposites, Springer Nature.","DOI":"10.1007\/978-3-030-05327-7_2"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Su\u00e1rez, M., Fern\u00e1ndez, A., Men\u00e9ndez, J.L., Torrecillas, R., Kessel, H.U., Hennicke, J., Kirchner, R., and Kessel, T. (2013). Challenges and Opportunities for Spark Plasma Sintering: A Key Technology Form a New Generation of Materials, INTECH Open Access Publisher. Chapter 13.","DOI":"10.5772\/53706"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"103291","DOI":"10.1016\/j.micron.2022.103291","article-title":"Microstructure and oxidation behavior of CoCrxCuFeMnNi high-entropy alloys fabricated by vacuum hot-pressing sintering","volume":"158","author":"Ren","year":"2022","journal-title":"Micron"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"971","DOI":"10.1007\/s11837-021-05109-8","article-title":"Processing and characterization of a mechanically alloyed and hot press sintered high entropy alloy from the Al-Cr-Fe-Mn-Mo family","volume":"74","author":"Stasiak","year":"2022","journal-title":"Miner. Met. Mater. Soc."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1016\/j.msea.2014.08.018","article-title":"Microstructure and mechanical properties of Ti\u201322Al\u201325Nb alloy fabricated by vacuum hot pressing sintering","volume":"616","author":"Jia","year":"2014","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"111637","DOI":"10.1016\/j.vacuum.2022.111637","article-title":"Influence of the vacuum hot pressing process on the microstructure, mechanical properties, and material characteristics of CrCoNiTa3 alloys","volume":"207","author":"Chang","year":"2023","journal-title":"Vacuum"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"742","DOI":"10.1016\/j.jallcom.2018.10.168","article-title":"Microstructure and mechanical properties of FeCoCrNiMnAlx high-entropy alloys prepared by mechanical alloying and hot-pressed sintering","volume":"775","author":"Cheng","year":"2019","journal-title":"J. Alloys Compd."},{"key":"ref_23","unstructured":"Seetharaman, S. (2014). Chapter 3.3\u2014Ellingham Diagram. Treatise on Process Metallurgy, Elsevier."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"747","DOI":"10.1007\/s11661-012-1464-2","article-title":"Vacuum Evaporation of Pure Metals","volume":"44","author":"Safarian","year":"2013","journal-title":"Metall. Mater. Trans. A"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1127","DOI":"10.1016\/S1875-5372(13)60074-0","article-title":"AlNiCrFexMo0.2CoCu high entropy alloys prepared by powder metallurgy","volume":"42","author":"Yuhu","year":"2013","journal-title":"Rare Met. Mater. Eng."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"246","DOI":"10.1016\/j.jallcom.2012.12.071","article-title":"Microstructure and properties of AlCrFeNiCoCu high entropy alloy prepared by powder metallurgy","volume":"555","author":"Qiu","year":"2013","journal-title":"J. Alloys Compd."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1016\/j.matlet.2018.01.092","article-title":"Effect of alloying order on non-isothermal sintering kinetics of mechanically alloyed high entropy alloy powders","volume":"217","author":"Mane","year":"2018","journal-title":"Mater. Lett."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"318","DOI":"10.1016\/j.msea.2003.08.028","article-title":"Sintering in different atmospheres of T15 and M2 high speed steels produced by a modified metal injection moulding process","volume":"366","author":"Levenfeld","year":"2004","journal-title":"Mater. Sci. Eng."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1002\/adem.201100269","article-title":"Hydrogen argon sintering of titanium to produce high density fine grain titanium alloys","volume":"14","author":"Fang","year":"2012","journal-title":"Adv. Eng. Mater."},{"key":"ref_30","first-page":"131","article-title":"The effect of the atmosphere and the role of pore filling on the sintering of aluminium","volume":"54","author":"Schaffer","year":"2006","journal-title":"Acta Mater."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/j.msea.2007.06.002","article-title":"Dimensional behaviour of aluminium sintered in different atmospheres","volume":"478","author":"Pieczonka","year":"2008","journal-title":"Mater. Sci. Eng."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"829","DOI":"10.1002\/adem.201000038","article-title":"Sintering of magnesium","volume":"12","author":"Wolff","year":"2010","journal-title":"Adv. Eng. Mater."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/S0925-8388(96)02679-5","article-title":"Removal of oxygen and nitrogen from niobium by external gettering","volume":"248","author":"Yong","year":"1997","journal-title":"J. Alloys Compd."},{"key":"ref_34","unstructured":"Palka, K., Pokrowiecki, R., and Krzywicka, M. (2019). Titanium for Consumer Applications, Elsevier."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"920","DOI":"10.1007\/s11837-016-1819-z","article-title":"The role of oxygen transfer in sintering of low alloy steel powder compacts: A review of the \u2018\u2018Internal Getter\u2019\u2019 Effect","volume":"68","author":"Christian","year":"2016","journal-title":"JOM"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"365","DOI":"10.1016\/0925-4005(91)80137-9","article-title":"Fundamentals and principles of potentiometric gas sensors based upon solid electrolytes","volume":"4","author":"Wolfgang","year":"1991","journal-title":"Sens. Actuators B Chem."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1564","DOI":"10.1557\/JMR.1992.1564","article-title":"An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments","volume":"7","author":"Oliver","year":"1992","journal-title":"Mater. Res. Soc."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1016\/j.msea.2017.01.096","article-title":"Nanoindentation and wear properties of Ti and Ti-TiB composite materials produced by selective laser melting","volume":"688","author":"Attar","year":"2017","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_39","unstructured":"(2024). Powder Diffraction File (PDF) Database 2024, International Centre for Diffraction Data."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"108518","DOI":"10.1016\/j.corsci.2020.108518","article-title":"Effect of Cr\/Mo carbides on corrosion behaviour of Fe_Mn_C twinning induced plasticity steel","volume":"167","author":"Hongxia","year":"2020","journal-title":"Corros. Sci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"2467","DOI":"10.1007\/BF02645474","article-title":"Sintering atmosphere effects on tensile properties of heavy alloys","volume":"19","author":"Bose","year":"1988","journal-title":"Metall. Trans. A"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s11249-016-0805-5","article-title":"Indentation hardness measurements at macro-, micro-, and nanoscale: A critical overview","volume":"65","author":"Broitman","year":"2017","journal-title":"Tribol. Lett."},{"key":"ref_43","unstructured":"German, R.M. (2014). Sintering: From Empirical Observations to Scientific Principles, Elsevier."},{"key":"ref_44","unstructured":"Kang, S.L. (2005). Densification, Grain Growth, and Microstructure, Elsevier."},{"key":"ref_45","first-page":"27","article-title":"Surface oxides in P\/M aluminum alloys","volume":"37","author":"Kim","year":"1985","journal-title":"J. Met."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"05013","DOI":"10.1051\/matecconf\/202032105013","article-title":"Achieving high strength and low Young\u2019s modulus by controlling the betastabilizers content in Ti-Nb-Ta-Zr-O alloys","volume":"321","author":"Preisler","year":"2020","journal-title":"MATEC Web Conf."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/17\/22\/5457\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T16:28:46Z","timestamp":1760113726000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/17\/22\/5457"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,11,8]]},"references-count":46,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2024,11]]}},"alternative-id":["ma17225457"],"URL":"https:\/\/doi.org\/10.3390\/ma17225457","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,11,8]]}}}