Probing the small-scale impact deformation mechanism in an aluminum single-crystal  

作　　者：Kehua Wang Jian Chen Yanhuai Li Xiyu Zhang Ben.D.Beake 

机构地区：[1]Jiangsu Key Laboratory of Advanced Metallic Materials,School of Materials Science and Engineering,Southeast University,Nanjing,211189,China [2]State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University,Xi’an,710049,China [3]Micro Materials Ltd,Willow House,Yale Business Village,Ellice Way,Wrexham,LL137YL,UK

出　　处：《Journal of Materials Science & Technology》2024年第20期212-220,共9页材料科学技术（英文版）

基　　金：This work was supported by the National Natural Science Foun-dation of China(No.52371058);the Ministry of Science and Tech-nology of the People’s Republic of China(No.2019YFE0191500);the State Key Laboratory for Mechanical Behavior of Materials(No.20222406).

摘　　要：Although the rate-dependence of metals has been widely researched,the deformation mechanism under small-scale impact conditions lacked exploration and in-depth understanding.Using quasi-static nanoin-dentation(strain rate,SR,<1 s^(-1))and high strain-rate nano-impact(SR>10^(3)s^(-1))with a pyramidal Berkovich tip,this study investigates the influence of SR on the deformation response of an aluminium single crystal(110).The underlying microstructural variance was analyzed using on-axis TKD and TEM.The results show that the impact deformation involves great elastic recovery and different substructural characteristics.In contrast to the uniform sub-grain substructure with medium and high-angle grain boundaries formed during quasi-static indentation,the substructure formed under impact has a more heterogeneous nature including microbands near the surface and sub-grains underneath with dominant low-angle grain boundaries.The significant change in substructure for the impact deformation comes from suppressed thermally activated dislocation motion,leading to the conversion of dislocation glide from wave-like(quasi-static)to planar regime(impacting),and the insufficient rearrangement of geomet-rically necessary dislocations(GNDs).The heterogeneous microstructure develops due to the competition between high strain-rate-induced planar-slip and strain gradient-induced GND rearrangement,as well as the uneven distribution of SR and strain gradient.Moreover,the underlying incipient mechanism of the microband is proposed,in which successive primary dislocations are nucleated at the surface and glide perpendicular to flanks to pile up.Finally,the influence of SR on indentation size effects is discussed.

关 键 词：NANOINDENTATION Nano-impact Microstructure Aluminum single crystal MICROBANDS Dislocations 

分 类 号：TB33[一般工业技术—材料科学与工程]