Strengthening-softening transition and maximum strength in Schwarz nanocrystals  

作　　者：Hanzheng Xing Jiaxi Jiang Yujia Wang Yongpan Zeng Xiaoyan Li 

机构地区：[1]Center for Advanced Mechanics and Materials,Applied Mechanics Laboratory,Department of Engineering Mechanics,Tsinghua University,Beijing,100084,China [2]Institute of High Performance Computing(IHPC),Agency for Science,Technology and Research(A*STAR),Singapore,138632,Singapore

出　　处：《Nano Materials Science》2024年第3期320-328,共9页纳米材料科学（英文版）

基　　金：the financial support from National Natural Science Foundation of China (Grants Nos.12325203,91963117,and 11921002)。

摘　　要：Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with nanosized Schwarz crystals exhibited high strength and excellent thermal stability.However,the grainsize effect and associated deformation mechanisms of Schwarz nanocrystals remain unknown.Here,we performed large-scale atomistic simulations to investigate the deformation behaviors and grain-size effect of nanocrystalline Cu with Schwarz crystals.Our simulations showed that similar to regular nanocrystals,Schwarz nanocrystals exhibit a strengthening-softening transition with decreasing grain size.The critical grain size in Schwarz nanocrystals is smaller than that in regular nanocrystals,leading to a maximum strength higher than that of regular nanocrystals.Our simulations revealed that the softening in Schwarz nanocrystals mainly originates from TB migration(or detwinning)and annihilation of GBs,rather than GB-mediated processes(including GB migration,sliding and diffusion)dominating the softening in regular nanocrystals.Quantitative analyses of simulation data further showed that compared with those in regular nanocrystals,the GB-mediated processes in Schwarz nanocrystals are suppressed,which is related to the low volume fraction of amorphous-like GBs and constraints of TB networks.The smaller critical grain size arises from the suppression of GB-mediated processes.

关 键 词：Schwarz nanocrystal Curved grain boundary Atomistic simulation Grain size effect Maximum strength 

分 类 号：TG146.11[一般工业技术—材料科学与工程] TB383.1[金属学及工艺—金属材料]