期刊
ACTA MATERIALIA
卷 96, 期 -, 页码 24-36出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2015.06.014
关键词
Nano-laminated structure; Surface mechanical grinding treatment (SMGT); Strain gradient; Nanometals
资金
- Ministry of Science and Technology of China [2012CB932201]
- National Natural Science Foundation of China [51231006, 51171182]
- Danish-Chinese center for Nanometals [51261130091, DNRF86-5]
- Chinese Academy of Sciences [KGZD-EW-T06]
A polycrystalline Ni (99.882% purity) bar sample was subjected to surface mechanical grinding treatment (SMGT) at ambient temperature. Gradient microstructures along depth from the treated surface were generated owing to a graded variation of strain and strain rates, including dislocation structures, submicron-sized structures, and nanostructures, respectively. In the subsurface layer of 10-80 mu m deep, 2-dimensional laminated structures with low angle boundaries and strong deformation textures were formed of which the average thickness is similar to 20 nm, one order of magnitude smaller than that of the ultrafine structures in Ni induced by conventional severe plastic deformation. The extraordinary grain refinement was ascribed to the high strain rates and high strain gradients that enhance accumulation of geometric necessary dislocations with a suppressed recovery dynamics. Deformation of the nano-laminated structures is governed by dislocation slip, and supplemented by deformation twining at the nanoscale, eventually leading to fragmentation into nano-sized equiaxed grains. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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