{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T03:37:13Z","timestamp":1792121833598,"version":"4.4.0"},"reference-count":49,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2020,2,18]],"date-time":"2020-02-18T00:00:00Z","timestamp":1581984000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>There is a strong demand for materials with inherently high creep resistance in the harsh environment of next-generation nuclear reactors. High entropy alloys have drawn intense attention in this regard due to their excellent elevated temperature properties and irradiation resistance. Here, the time-dependent plastic deformation behavior of two refractory high entropy alloys was investigated, namely HfTaTiVZr and TaTiVWZr. These alloys are based on reduced activity metals from the 4-5-6 elemental palette that would allow easy post-service recycling after use in nuclear reactors. The creep behavior was investigated using nano-indentation over the temperature range of 298 K to 573 K under static and dynamic loads up to 5 N. Creep stress exponent for HfTaTiVZr and TaTiVWZr was found to be in the range of 20\u2013140 and the activation volume was ~16\u201320b3, indicating dislocation dominated mechanism. The stress exponent increased with increasing indentation depth due to a higher density of dislocations and their entanglement at larger depth and the exponent decreased with increasing temperature due to thermally activated dislocations. Smaller creep displacement and higher activation energy for the two high entropy alloys indicate superior creep resistance compared to refractory pure metals like tungsten.<\/jats:p>","DOI":"10.3390\/e22020230","type":"journal-article","created":{"date-parts":[[2020,2,19]],"date-time":"2020-02-19T04:06:01Z","timestamp":1582085161000},"page":"230","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":40,"title":["High-Temperature Nano-Indentation Creep of Reduced Activity High Entropy Alloys Based on 4-5-6 Elemental Palette"],"prefix":"10.3390","volume":"22","author":[{"given":"Maryam","family":"Sadeghilaridjani","sequence":"first","affiliation":[{"name":"Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Saideep","family":"Muskeri","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mayur","family":"Pole","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1954-0045","authenticated-orcid":false,"given":"Sundeep","family":"Mukherjee","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,2,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"735","DOI":"10.1016\/j.actamat.2012.11.004","article-title":"Materials challenges in nuclear energy","volume":"61","author":"Zinkle","year":"2013","journal-title":"Acta Mater."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1016\/j.jnucmat.2008.08.044","article-title":"Structural materials for Gen-IV nuclear reactors: Challenges and opportunities","volume":"383","author":"Murty","year":"2008","journal-title":"J. Nucl. Mater."},{"key":"ref_3","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_4","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.pmatsci.2013.10.001","article-title":"Microstructures and properties of high entropy alloys","volume":"61","author":"Zhang","year":"2014","journal-title":"Prog. Mater. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"151955","DOI":"10.1016\/j.jnucmat.2019.151955","article-title":"Ion irradiation response and mechanical behavior of reduced activity high entropy alloy","volume":"529","author":"Sadeghilaridjani","year":"2020","journal-title":"J. Nucl. Mater."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1758","DOI":"10.1016\/j.intermet.2010.05.014","article-title":"Refractory high entropy alloys","volume":"18","author":"Senkov","year":"2010","journal-title":"Intermetallics"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"6043","DOI":"10.1016\/j.jallcom.2011.02.171","article-title":"Microstructure and room temperature properties of a high entropy TaNbHfZrTi alloy","volume":"509","author":"Senkov","year":"2011","journal-title":"J. Alloys Compd."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"698","DOI":"10.1016\/j.intermet.2011.01.004","article-title":"Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys","volume":"19","author":"Senkov","year":"2011","journal-title":"Intermetallics"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1016\/j.mtla.2018.09.014","article-title":"Low activation high entropy alloys for next generation nuclear applications","volume":"4","author":"Ayyagari","year":"2018","journal-title":"Materialia"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1007\/s11661-005-0142-z","article-title":"Creep deformation characteristics of tin and tin-based electronic solder alloys","volume":"36","author":"Mathew","year":"2005","journal-title":"Metall. Mater. Trans. A"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"12658","DOI":"10.1038\/s41598-017-13026-7","article-title":"The High Temperature Tensile and Creep Behaviors of High Entropy Superalloy","volume":"7","author":"Tsao","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Cao, C., Fu, J., Tong, T., Hao, Y., Gu, P., Hao, H., and Peng, L. (2018). Intermediate-Temperature Creep Deformation and Microstructural Evolution of an Equiatomic FCC-Structured CoCrFeNiMn High-Entropy Alloy. Entropy, 20.","DOI":"10.3390\/e20120960"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.ijplas.2012.08.008","article-title":"Nanoscale room temperature creep of nanocrystalline nickel pillars at low stresses","volume":"41","author":"Choi","year":"2013","journal-title":"Int. J. Plast."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Mridha, S., Komarasamy, M., Bhowmick, S., Mishra, R.S., and Mukherjee, S. (2018). Small-Scale Plastic Deformation of Nanocrystalline High Entropy Alloy. Entropy, 20.","DOI":"10.3390\/e20110889"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"395","DOI":"10.1016\/j.ijrmhm.2015.08.010","article-title":"Nanoindentation study on the creep characteristics of high-entropy alloy films: Fcc versus bcc structures","volume":"54","author":"Ma","year":"2016","journal-title":"Int. J. Refract. Metals Hard Mater."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1177","DOI":"10.1557\/jmr.2013.39","article-title":"An improved long-term nanoindentation creep testing approach for studying the local deformation processes in nanocrystalline metals at room and elevated temperatures","volume":"28","author":"Maier","year":"2013","journal-title":"J. Mater. Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/j.actamat.2016.03.032","article-title":"A direct comparison of high temperature nanoindentation creep and uniaxial creep measurements for commercial purity aluminum","volume":"111","author":"Oliver","year":"2016","journal-title":"Acta Mater."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"138326","DOI":"10.1016\/j.msea.2019.138326","article-title":"Strain rate sensitivity of a novel refractory high entropy alloy: Intrinsic versus extrinsic effects","volume":"766","author":"Sadeghilaridjani","year":"2019","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3466","DOI":"10.1007\/s11837-019-03703-5","article-title":"Strain Gradient Plasticity in Multiprincipal Element Alloys","volume":"71","author":"Sadeghilaridjani","year":"2019","journal-title":"JOM"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2296","DOI":"10.1007\/s11837-015-1566-6","article-title":"Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy","volume":"67","author":"Mridha","year":"2015","journal-title":"JOM"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Mridha, S., Sadeghilaridjani, M., and Mukherjee, S. (2019). Activation Volume and Energy for Dislocation Nucleation in Multi-Principal Element Alloys. Metals, 9.","DOI":"10.3390\/met9020263"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"505","DOI":"10.1016\/j.msea.2011.11.016","article-title":"Nanoindentation creep of tin and aluminium: A comparative study between constant load and constant strain rate methods","volume":"532","author":"Shen","year":"2012","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"5489","DOI":"10.1016\/j.actamat.2006.07.020","article-title":"A critical appraisal of the extraction of creep parameters from nanoindentation data obtained at room temperature","volume":"54","author":"Goodall","year":"2006","journal-title":"Acta Mater."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1108\/17579861311303618","article-title":"A study on time dependent properties of aluminum alloy by nanoindentation technique","volume":"4","author":"Charitidis","year":"2013","journal-title":"Int. J. Struct. Integ."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"993","DOI":"10.1557\/jmr.2009.0106","article-title":"Indentation creep of a Ti-based metallic glass","volume":"24","author":"Huang","year":"2009","journal-title":"J. Mater. Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.msea.2007.06.015","article-title":"The characterization of creep and time-dependent properties of bulk metallic glasses using nanoindentation","volume":"478","author":"Li","year":"2008","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"314","DOI":"10.1016\/j.actamat.2016.02.049","article-title":"Spherical nanoindentation creep behavior of nanocrystalline and coarse-grained CoCrFeMnNi high-entropy alloys","volume":"109","author":"Lee","year":"2016","journal-title":"Acta Mater."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1016\/j.msea.2014.10.065","article-title":"Nanoindentation creep behavior in a CoCrFeCuNi high-entropy alloy film with two different structure states","volume":"621","author":"Ma","year":"2015","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1016\/j.intermet.2014.05.007","article-title":"Nanoindentation characterized initial creep behavior of a high-entropy-based alloy CoFeNi","volume":"53","author":"Wang","year":"2014","journal-title":"Intermetallics"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/j.jnoncrysol.2017.04.041","article-title":"Nanoindentation study on the room temperature creep characteristics of a senary Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7 high entropy bulk metallic glass","volume":"470","author":"Wang","year":"2017","journal-title":"J. Non-Cryst. Solids"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"3307","DOI":"10.1016\/j.surfcoat.2010.03.041","article-title":"Mechanical properties, deformation behaviors and interface adhesion of (AlCrTaTiZr)Nx multi-component coatings","volume":"204","author":"Chang","year":"2010","journal-title":"Surf. Coat. Tech."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"5871","DOI":"10.1007\/s11661-016-3469-8","article-title":"Nanoindentation Creep Behavior of an Al0.3CoCrFeNi High-Entropy Alloy","volume":"47","author":"Zhang","year":"2016","journal-title":"Metall. Mater. Trans. A"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"388","DOI":"10.1080\/02670836.2016.1185260","article-title":"Predicting the performance of tungsten in a fusion environment: A literature review","volume":"33","author":"Abernethy","year":"2017","journal-title":"Mater. Sci. Tech."},{"key":"ref_34","unstructured":"Forrest, R.A., Tabasso, A., Danani, C., Jakhar, S., and Shaw, A.K. (2009). Handbook of Activation Data Calculated Using EASY-2007, United Kingdom Atomic Energy Authority."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.actamat.2017.08.026","article-title":"Thermally activated dislocation plasticity in body-centered cubic chromium studied by high-temperature nanoindentation","volume":"140","author":"Choi","year":"2017","journal-title":"Acta Mater."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.matchar.2016.05.001","article-title":"Room temperature creep behavior of Ti\u2013Nb\u2013Ta\u2013Zr\u2013O alloy","volume":"118","author":"Zhang","year":"2016","journal-title":"Mater. Charact."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1080\/21663831.2017.1383946","article-title":"Nanoindentation creep behavior of Cu\u2013Zr metallic glass films","volume":"6","author":"Wang","year":"2018","journal-title":"Mater. Res. Lett."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Sawant, A., Tin, S., and Zhao, J.-C. (2008). High temperature nano-indentation of Ni-based superalloy. TMS Conf. Superalloys, 863\u2013871.","DOI":"10.7449\/2008\/Superalloys_2008_863_871"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"505","DOI":"10.1115\/1.2744430","article-title":"Effect of Strain Rate on the Dynamic Hardness in Metals","volume":"129","author":"Almasri","year":"2007","journal-title":"J. Eng. Mater. Tech."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"513","DOI":"10.1557\/jmr.2004.19.2.513","article-title":"Size effects of nanoindentation creep","volume":"19","author":"Li","year":"2004","journal-title":"J. Mater. Res."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1016\/j.matlet.2011.11.119","article-title":"Room temperature nanoindentation creep of nanocrystalline Cu and Cu alloys","volume":"70","author":"Liu","year":"2012","journal-title":"Mater. Lett."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.msea.2014.07.057","article-title":"Depth dependent strain rate sensitivity and inverse indentation size effect of hardness in body-centered cubic nanocrystalline metals","volume":"615","author":"Zhao","year":"2014","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1225","DOI":"10.1557\/JMR.2010.0159","article-title":"Temperature dependence of the indentation size effect","volume":"25","author":"Franke","year":"2010","journal-title":"J. Mater. Res."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1179","DOI":"10.1007\/BF02644330","article-title":"On the stress exponent and the rate-controlling mechanism of high-temperature creep in some solid solutions","volume":"5","author":"Oikawa","year":"1974","journal-title":"Met. Trans."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"5708","DOI":"10.1016\/j.actamat.2007.06.036","article-title":"Deformation kinetics of nanocrystalline nickel","volume":"55","author":"Li","year":"2007","journal-title":"Acta Mater."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"4114","DOI":"10.1007\/s10854-016-6031-y","article-title":"Creep behavior of Sn\u2013Bi solder alloys at elevated temperatures studied by nanoindentation","volume":"28","author":"Shen","year":"2017","journal-title":"J. Mater. Sci. Mater. Electron."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Ginder, R.S., and Pharr, G.M. (2019). Characterization of power-law creep in the solid-acid CsHSO4 via nanoindentation. J. Mater. Res., 1130\u20131137.","DOI":"10.1557\/jmr.2018.505"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1080\/21663831.2018.1543731","article-title":"Dislocation creep behavior of CoCrFeMnNi high entropy alloy at intermediate temperatures","volume":"6","author":"Kang","year":"2018","journal-title":"Mater. Res. Lett."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1016\/j.msea.2017.01.027","article-title":"High-temperature plastic flow of a precipitation-hardened FeCoNiCr high entropy alloy","volume":"686","author":"He","year":"2017","journal-title":"Mater. Sci. Eng. A"}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/22\/2\/230\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T08:58:53Z","timestamp":1760173133000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/22\/2\/230"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,2,18]]},"references-count":49,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2020,2]]}},"alternative-id":["e22020230"],"URL":"https:\/\/doi.org\/10.3390\/e22020230","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,2,18]]}}}