An ultra-strong and ductile crystalline-amorphous nanostructured surface layer on TiZrHfTaNb0.2 high-entropy alloy by laser surface processing

Heterogeneous crystalline-amorphous nanostructures have been documented to show superior strength -ductility synergy via the co-deformation cooperative effects of nanograins and amorphous grain bound-aries. In this work, a facile laser surface remelting technique with rapid cooling rate was successfully developed to fabricate a ti 100 gm-thick gradient nanostructured layer accompanied by phase decompo-sition on a TiZrHfTaNb0.2 high-entropy alloy, where a ti 5 gm-thick crystalline-amorphous nanostruc-tured top surface layer with an average grain size of ti 7 nm was obtained. Such crystalline -amorphous nanostructured layer shows an ultrahigh yield strength of ti 6.0 GPa and a compression strain of ti 25 % during the localized micro-pillar compression tests. The atomic observations reveal that co -deformation cooperative mechanisms include the well-retained dislocation activities in nanograins but crystallization in amorphous grain boundaries, which subsequently lead to the grain coarsening via grain boundary-mediated plasticity. This study sheds light on the development of high-performance high-entropy alloys with novel crystalline-amorphous nanostructures and provides significant insight into their plastic deformation mechanisms.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Heterogeneous crystalline-amorphous nanostructures exhibit superior strength-ductility synergy through the cooperative effects of nanograins and amorphous grain boundaries in co-deformation. In this study, a facile laser surface remelting technique was successfully developed to fabricate a 100 μm-thick gradient nanostructured layer with phase decomposition on a TiZrHfTaNb0.2 high-entropy alloy. A 5 μm-thick crystalline-amorphous nanostructured surface layer with an average grain size of 7 nm was obtained. This nanostructured layer demonstrated an ultrahigh yield strength of 6.0 GPa and a compression strain of 25% during localized micro-pillar compression tests. Co-deformation cooperative mechanisms observed included well-retained dislocation activities in nanograins and crystallization in amorphous grain boundaries, resulting in grain coarsening through grain boundary-mediated plasticity. This study provides insights into the development of high-performance high-entropy alloys with novel crystalline-amorphous nanostructures and their plastic deformation mechanisms.