Realizing high work hardening and thus elevated strength-ductility synergy are prerequisites for the practical usage of body-centered-cubic high entropy alloys(BCC-HEAs).In this study,we report a novel dynamic strengthening mechanism,martensitic twinning transformation mechanism in a metastable re-fractory element-based BCC-HEA(TiZrHf)87Ta13(at.％)that can profoundly enhance the work hardening capability,leading to a large uniform ductility and high strength simultaneously.Different from con-ventional transformation induced plasticity(TRIP)and twinning induced plasticity(TWIP)strengthen-ing mechanisms,the martensitic twinning transformation strengthening mechanism combines the best characteristics of both TRIP and TWIP strengthening mechanisms,which greatly alleviates the strength-ductility trade-off that ubiquitously observed in BCC structural alloys.Microstructure characterization,carried out using X-ray diffraction(XRD)and electron back-scatter diffraction(EBSD)shows that,upon straining,α"(orthorhombic)martensite transformation,self-accommodation(SA)α"twinning and me-chanical α"twinning were activated sequentially.Transmission electron microscopy(TEM)analyses re-veal that continuous twinning activation is inherited from nucleating mechanical{351}α"type Ⅰ twins within SA"{351}"<(2)11>α"type Ⅱ twinned α"variants on[351}α"twinning plane by twinning transfor-mation through simple shear,thereby accommodating the excessive plastic strain through the twinning shear while concurrently refining the grain structure.Consequently,consistent high work hardening rates of 2-12.5 GPa were achieved during the entire plastic deformation,leading to a high tensile strength of 1.3 GPa and uniform elongation of 24％.Alloy development guidelines for activating such martensitic twinning transformation strengthening mechanism were proposed,which could be important in devel-oping new BCC-HEAs with optimal mechanical performance.

Yuhe Huang;Junheng Gao;Vassili Vorontsov;Dikai Guan;Russell Goodall;David Dye;Shuize Wang;Qiang Zhu;W.Mark Rainforth;Iain Todd

Department of Materials Science and Engineering,University of Sheffield,Sheffield S1 3JD,United Kingdom;Department of Mechanical and Energy Engineering,Southern University of Science and Technology,Shenzhen,518055,China;Beijing Advanced Innovation Center for Materials Genome Engineering,University of Science and Technology Beijing,Beijing 100083,China;Department of Materials,Royal School of Mines,Imperial College London,London SW7 2BP,United Kingdom

材料科学技术（英文版）

[1]Yuhe Huang;Junheng Gao;Vassili Vorontsov;Dikai Guan;Russell Goodall;David Dye;Shuize Wang;Qiang Zhu;W.Mark Rainforth;Iain Todd-.Martensitic twinning transformation mechanism in a metastable IVB element-based body-centered cubic high-entropy alloy with high strength and high work hardening rate)[J].材料科学技术（英文版）,2022(29):217-231

fractory,TiZrHf,87Ta13

Martensitic,twinning,transformation,metastable,IVB,element,body,centered,cubic,high,entropy,work,hardening,Realizing,thus,elevated,ductility,synergy,are,prerequisites,practical,usage,alloys,BCC,HEAs,In,this,study,report,novel,dynamic,strengthening,martensitic,that,can,profoundly,enhance,capability,leading,large,uniform,simultaneously,Different,from,ventional,induced,plasticity,TRIP,TWIP,mechanisms,combines,best,characteristics,both,which,greatly,alleviates,trade,off,ubiquitously,observed,structural,Microstructure,characterization,carried,out,using,ray,diffraction,electron,back,scatter,EBSD,shows,upon,straining,orthorhombic,martensite,self,accommodation,SA,were,activated,sequentially,Transmission,microscopy,TEM,analyses,veal,continuous,activation,inherited,nucleating,mechanical,type,twins,within,twinned,variants,plane,through,simple,shear,thereby,accommodating,excessive,while,concurrently,refining,grain,Consequently,consistent,rates,GPa,achieved,during,entire,deformation,tensile,elongation,Alloy,development,guidelines,activating,such,proposed,could,important,oping,new,optimal,performance

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