Abstract
Heterogeneous gradient nanostructured metals have been shown to achieve the strength-ductility syn-ergy,thus potentially possessing the enhanced tribological performance in comparison with their homo-geneous nanograined counterparts.In this work,a facile laser surface remelting-based surface treatment technique is developed to fabricate a gradient nanostructured layer on a TiZrHfTaNb refractory high-entropy alloy.The characterization of the microstructural evolution along the depth direction from the matrix to the topmost surface layer shows that the average grain size in the～100 μm-thick gradient nanostructured layer is dramatically refined from the original～200 μm to only～8 nm in the top sur-face layer.The microhardness is therefore gradually increased from～240 HV in matrix to～650 HV in the topmost surface layer,approximately 2.7 times.Noticeably,the original coarse-grained single-phase body-centered-cubic TiZrHfTaNb refractory high-entropy alloy is gradually decomposed into TiNb-rich body-centered-cubic phase,TaNb-rich body-centered-cubic phase,ZrHf-rich hexagonal-close-packed phase and TiZrHf-rich face-centered-cubic phase with gradient distribution in grain size along the depth direction during the gradient refinement process.As a result,the novel laser surface treatment-introduced gra-dient nanostructured TiZrHfTaNb refractory high-entropy alloy demonstrates the significantly improved wear resistance,with the wear rate reducing markedly by an order of magnitude,as compared with the as-cast one.The decomposed multi-phases and gradient nanostructures should account for the enhanced wear resistance.Our findings provide new insights into the refinement mechanisms of the laser-treated refractory high-entropy alloys and broaden their potential applications via heterogeneous gradient nanos-tructure engineering.
基金项目
joint PhD project between the Hong Kong Polytechnic University and Southern University of Science and Technology()
Research Commit-tee of PolyU under student account code(RK2N)
国家自然科学基金(51701171)
国家自然科学基金(51971187)
Fundamental Re-search Program of Shenzhen(JCYJ20170412153039309)
维普
万方数据