文献类型：期刊文献

英文题名：Bending stress relaxation of microscale single-crystal copper at room temperature: An in situ SEM study

作者：Chen, Wufan[1,3];Wang, Xiaoyuan[2];Yan, Yabin[2];Sumigawa, Takashi[3];Kitamura, Takayuki[3];Feng, Miaolin[4];Xuan, Fu-Zhen[2]

机构：[1]Zhejiang Univ, Sch Aeronaut & Astronaut, Hangzhou 310058, Peoples R China;[2]East China Univ Sci & Technol, Key Lab Pressure Syst & Safety, Minist Educ, Sch Mech & Powering Engn, Shanghai 200237, Peoples R China;[3]Kyoto Univ, Dept Mech Engn & Sci, Nishikyo Ku, Kyoto 6158540, Japan;[4]Shanghai Jiao Tong Univ, State Key Lab Ocean Engn, Sch Naval Architecture Ocean & Civil Engn, Shanghai 200240, Peoples R China

年份：2021

卷号：90

外文期刊名：EUROPEAN JOURNAL OF MECHANICS A-SOLIDS

收录：;EI(收录号：20213110701766);WOS:【SCI-EXPANDED(收录号:WOS:000686044600009)】；

基金：This work was supported by the National Natural Science Foundation of China (NO. 11602252, 51835003) , the Specialized Research Fund for the Doctoral Program of Higher Education of China (2013007310057) , Natural Science Foundation of Shanghai (Grant No. 19ZR1413200) , Fundamental Research Funds for the Cornell University (Grant No. 50321071915017) , Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, China Postdoctoral Science Foundation (Grant No. 2020M671705) , JSPS KAKENHI (Grant Nos. 18H03753, 18H05241, 20K20963) , and the Society for the Promotion of Science (Grant No. JPH05241) .

语种：英文

外文关键词：In situ SEM bending; Stress relaxation; Strain gradient; Dislocation pile-up; Activation volume; Size effect

摘要：The bending stress relaxation of microscale single-crystal copper was studied by in situ SEM bending experiments to elucidate the time-dependent plasticity involving the effect of the strain gradient and the sample size. Three specimens with varied heights of square cross sections were fabricated using a focused ion beam. Interestingly, an obvious bending plateau was observed in the load-displacement curves. The calculated flow stress on the cross section indicated an inverse relationship between the specimen size and strength. In addition, the proportion of decay stress is approximately 2.7% for the beam with a height of h = 1.82 mu m and 13.9% for that of h = 0.94 mu m in the bending plateau. Moreover, during the dwell period, a sudden stress drop occurred, which is ascribed to the strain burst or stress jerky during the deformation of single-crystal metals. Microbending is usually related to a significant increase in geometrically necessary dislocations (GNDs), which is supposed to improve the resistance for further deformation. However, the bending plateau implied perfect plastic flow and an evolving balance in the microstructures. On the other hand, thermal activation theory was employed to interpret the time dependent plasticity. The apparent activation volume of the dwell periods in the bending plateau suggested that cross slip dominates the inelastic strain rate evolution. Finally, the inelastic strain rate for stress relaxation was derived from the curve of decay stress, and it was inversely proportional to the height of the microbeam, which is in complete contrast with the trend observed in the previous compression tests of micropillars. In current microscale bending specimens, the thinner beam containing fewer initial dislocation sources exhibits a larger creep ductility with the assistance of GNDs.