title: Nanocrystalline High-Entropy Alloys: A New Paradigm in High-Temperature Strength and Stability.
abstract: Metals with nanometer-scale grains or nanocrystalline metals exhibit high strengths at ambient conditions, yet their strengths substantially decrease with increasing temperature, rendering them unsuitable for usage at high temperatures. Here, we show that a nanocrystalline high-entropy alloy (HEA) retains an extraordinarily high yield strength over 5 GPa up to 600 °C, 1 order of magnitude higher than that of its coarse-grained form and 5 times higher than that of its single-crystalline equivalent. As a result, such nanostructured HEAs reveal strengthening figures of merit-normalized strength by the shear modulus above 1/50 and strength-to-density ratios above 0.4 MJ/kg, which are substantially higher than any previously reported values for nanocrystalline metals in the same homologous temperature range, as well as low strain-rate sensitivity of ∼0.005. Nanocrystalline HEAs with these properties represent a new class of nanomaterials for high-stress and high-temperature applications in aerospace, civilian infrastructure, and energy sectors.
authors.affiliation: Laboratory for Nanometallurgy, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Yu
authors.identifier: 0000-0002-0179-3642
authors.initials: Y
authors.lastname: Zou
authors.affiliation: Laboratory for Nanometallurgy, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Jeffrey M
authors.identifier: 0000-0001-7763-2610
authors.initials: JM
authors.lastname: Wheeler
authors.affiliation: Laboratory for Nanometallurgy, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Huan
authors.initials: H
authors.lastname: Ma
authors.affiliation: Laboratory for Nanometallurgy, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Okle
authors.affiliation: Laboratory for Nanometallurgy, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Ralph
authors.initials: R
authors.lastname: Spolenak
keywords: High-entropy alloys; grain boundary; high temperature; nanocrystalline; stability; strength