期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2019.03.020
关键词
Gradient copper; Ductility; Softening and hardening; Grain growth; Back stress
类别
资金
- National Natural Science Foundation of China [11672195, 51741106, 51301092]
- Sichuan Youth Science and Technology Foundation [2016JQ0047]
A gradient-structured Cu sample composed of grain-size gradient surface layer (GSL) and homogeneous coarse-grained (CG) core was fabricated by surface severe plastic deformation. Microhardness measurements revealed that both tension-induced softening in the top nanograined surface layer and hardening in the subsurface layer of integrated gradient sample were far more pronounced than that of a freestanding GSL, i.e. extraordinary softening and hardening occurred in gradient sample. The synergetic deformation between GSL and CG core produced accumulation of geometrically necessary dislocations and thereby back stress strengthening, resulting in extra flow stress and hardening. The extraordinary softening was attributed to the extra flow stress-assisted grain coarsening in nanograined layer. Furthermore, strain measurements proved that the CG matrix plays critical roles in stabilizing the grain coarsening and homogenizing the strain distribution in nanograined layer, which were favorable for the uniform ductility.
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