摘要
Refractory high-entropy alloys(HEAs)possess many useful properties such as high strength and high-temperature stability.So far,most studies on refractory HEAs have been limited to a few well-known compositions and on their coarse-grain bulk forms.Here we fabricate nanocrystalline(TiZrHf)_(x)(NbTa)_(1−x)HEA thin films with a large range of compositions(x=0.07–0.90)by the direct current(DC)magnetron co-sputtering technique and measure their mechanical properties using the nanoindentation method.All the as-deposited HEA thin films show a solid-solution body-centered cubic(bcc)structure.As the compositional ratio(x)increases,the elastic modulus decreases from 153 to 123 GPa,following the trend of the rule of mixture.As x increases,the hardness first decreases from 6.5 GPa(x=0.07)to the lowest value(4.6 GPa,x=0.48)and then increases to the highest value(7.1 GPa,x=0.90),showing a concave trend.The change in hardness might be attributed to the combinational influence caused by the atomic size and modulus effects,as well as the texture effect.The authors also propose a few open questions for future studies on this and related HEA systems.
基金
support from the Discovery Grants Program(No.RGPIN-2018-05731)
the Natural Sciences and Engineering Research Council of Canada(NSERC)
New Frontiers in Research Fund-Exploration(No.NFRFE-2019-00603)
Dean’s Spark Assistant Professorship in the Faculty of Applied Science&Engineering at
University of Toronto.M.J.R.H.acknowledges the financial support from Vanier Canada Graduate Scholarship(NSERC),Ontario Graduate Scholarship,and Queen Elizabeth II/Eleanor and Burnett Thall Graduate Scholarship
Canada Foundation for Innovation(CFI)-John R.Evans Leaders Fund(JELF)Project#38044.
