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.

Jiasi Luo;Wanting Sun;Ranxi Duan;Wenqing Yang;K.C.Chan;Fuzeng Ren;Xu-Sheng Yang

Department of Industrial and Systems Engineering,Advanced Manufacturing Technology Research Centre,The Hong Kong Polytechnic University,Hung Hom,Kowloon,Hong Kong,China;Department of Materials Science and Engineering,Southern University of Science and Technology,Shenzhen 518055,China;The Hong Kong Polytechnic University Shenzhen Research Institute,Shenzhen 518060,China

材料科学技术（英文版）

[1]Jiasi Luo;Wanting Sun;Ranxi Duan;Wenqing Yang;K.C.Chan;Fuzeng Ren;Xu-Sheng Yang-.Laser surface treatment-introduced gradient nanostructured TiZrHfTaNb refractory high-entropy alloy with significantly enhanced wear resistance)[J].材料科学技术（英文版）,2022(15):43-56

TiZrHfTaNb,TiNb,TaNb,ZrHf,TiZrHf

Laser,surface,treatment,introduced,gradient,nanostructured,refractory,high,entropy,significantly,enhanced,wear,resistance,Heterogeneous,metals,have,been,shown,achieve,strength,ductility,syn,ergy,thus,potentially,possessing,tribological,performance,comparison,their,homo,nanograined,counterparts,In,this,work,facile,laser,remelting,technique,developed,fabricate,layer,characterization,microstructural,evolution,along,depth,direction,from,matrix,topmost,shows,that,average,size,thick,dramatically,refined,original,only,microhardness,therefore,gradually,increased,HV,approximately,times,Noticeably,coarse,single,body,centered,cubic,decomposed,into,rich,hexagonal,close,packed,distribution,during,refinement,process,result,novel,demonstrates,improved,reducing,markedly,by,order,magnitude,compared,cast,one,multi,phases,nanostructures,should,account,Our,findings,provide,new,insights,mechanisms,treated,alloys,broaden,applications,via,heterogeneous,engineering

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