http://scholars.ntou.edu.tw/handle/123456789/18031
標題: | Investigation of nanotwins in the bimodal-structured Fe22Co22Ni20Cr22Mn14 alloy subjected to high-strain-rate deformation at cryogenic temperatures | 作者: | Tsai-Fu Chung Pin-Jung Chen Cheng-Ling Tai Po-Han Chiu Yo-Shiuan Lin Chien-Nan Hsiao Chih-Yuan Chen Shing-Hoa Wang Jien-Wei Yeh Woei-Shyan Lee Chin-Lung Kuo Jer-Ren Yang |
公開日期: | 十二月-2020 | 卷: | 170 | 起(迄)頁: | 110667 | 來源出版物: | Materials Characterization | 摘要: | Cold-rolling Fe22Co22Ni20Cr22Mn14 high entropy alloy (with a deformation of 70%), and annealing it at two temperatures (1100 and 800 °C) respectively created a bimodal grain size distribution in large-grain (LG) samples having an average grain size of 45.9 ± 20.0 μm and in small-grain (SG) samples having an average grain size of 4.3 ± 3.0 μm. Under three cryogenic temperatures (−50, −100, and −150 °C), high-speed deformation (~9 × 103 s−1) was conducted on a split Hopkinson pressure bar (SHPB) system to investigate the microstructural evolution of deformation nanotwins in the bimodal-structured samples. Subjected to high-speed deformation at decreasing cryogenic temperatures, the mechanical behaviors of LG samples were superior to those of SG samples. Notably, under high-speed deformation at −150 °C, LG structures achieved excellent mechanical strength of ~3.3 GPa with good ductility of ~31.9%. Profuse lamellar annealing nanotwins, which pre-existed in the coarse grains of LG samples, promoted efficient refinement strengthening. High-resolution transmission electron microscopy (HR-TEM) clearly revealed that the deformation nanotwins induced by high-speed deformation further refined the pre-existing annealing nanotwins in the coarse grains of LG samples, presumably providing advanced mechanical sustainability for high-speed deformation at cryogenic temperatures. It is suggested that the micrometer-scaled and nanometer-scaled annealing twins appear first in the matrices of coarse grains, enhancing the initial work-hardening; subsequently the deformation nanotwins form in pre-existing annealing nanotwins and narrow strips of the matrix, effectively providing the dynamic grain refinement and the work hardening capacity. |
URI: | http://scholars.ntou.edu.tw/handle/123456789/18031 | DOI: | 10.1016/j.matchar.2020.110667 |
顯示於: | 機械與機電工程學系 |
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