Nanocrystalline metals often display a high strength up to the gigapascal level,yet they suffer from poor plasticity.Previous studies have shown that the development of hetero-sized grains can efficiently over-come the strength-ductility trade-off of nanocrystalline metals.However,whether this strategy can lead to the fabrication of nanocrystalline nanowires exhibiting both high strength and superplasticity is un-clear,similar to the atomistic deformation mechanism.In this paper,we show that ultra-small nanocrys-talline Au nanowires comprising grains in both the Hall-Petch and inverse Hall-Petch grain-size regions can exhibit extremely high uniform elongation(236％)and high strength(2.34 gigapascals)at room tem-perature.In situ atomic-scale observations revealed that the plastic deformation underwent two stages.In the first stage,the super-elongation ability originated from the intergrain plasticity of small grains via mechanisms such as grain boundary migration and grain rotation.This intergrain plasticity caused the grains in the heterogeneous-structured nanowires to grow very large.In the second stage,the super-elongation ability originated from intragrain plasticity accompanied by the diffusion of surface atoms.Our results show that the hetero-grain-sized nanocrystalline nanowires,comprising grains with sizes both in the strongest Hall-Petch effect region and the inverse Hall-Petch effect region,were simultaneously ultra-strong and ductile.They displayed neither a strength-ductility trade-off nor plastic instability.

Libo Fu;Deli Kong;Chengpeng Yang;Jiao Teng;Yan Lu;Yizhong Guo;Guo Yang;Xin Yan;Pan Liu;Mingwei Chen;Ze Zhang;Lihua Wang;Xiaodong Han

Beijing Key Lab of Microstructure and Properties of Advanced Materials,Beijing University of Technology,Beijing 100124,China;Department of Material Physics and Chemistry,University of Science and Technology Beijing,Beijing 100083,China;School of Mechanical Engineering and Automation,Beihang University,Beijing 100191,China;School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Department of Materials Science and Engineering,Johns Hopkins University,Baltimore,MD 21218,United States;School of Materials Science and Engineering,Zhejiang University,Hangzhou 310027,China

材料科学技术（英文版）

[1]Libo Fu;Deli Kong;Chengpeng Yang;Jiao Teng;Yan Lu;Yizhong Guo;Guo Yang;Xin Yan;Pan Liu;Mingwei Chen;Ze Zhang;Lihua Wang;Xiaodong Han-.Ultra-high strength yet superplasticity in a hetero-grain-sized nanocrystalline Au nanowire)[J].材料科学技术（英文版）,2022(06):95-106

superplasticity,gigapascal,gigapascals,intergrain,intragrain

Ultra,high,strength,yet,sized,nanocrystalline,Au,Nanocrystalline,metals,often,level,they,suffer,from,poor,Previous,studies,have,shown,that,development,grains,can,efficiently,over,come,ductility,trade,off,However,whether,this,strategy,lead,fabrication,nanowires,exhibiting,both,clear,similar,atomistic,deformation,In,paper,ultra,small,comprising,Hall,Petch,inverse,regions,extremely,uniform,elongation,room,tem,perature,situ,atomic,scale,observations,revealed,underwent,two,stages,first,originated,via,mechanisms,such,boundary,migration,rotation,This,caused,heterogeneous,structured,grow,very,large,second,accompanied,by,diffusion,surface,atoms,Our,results,sizes,strongest,effect,were,simultaneously,ductile,They,displayed,neither,nor,instability

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