期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2014.02.008
关键词
Coarse-grained pure aluminum; Size effect; Pre-fatigue deformation; Tensile property; Fracture; Sub-structure
类别
资金
- National Natural Science Foundation of China (NSFC) [51071041, 51271054, 51231002]
- Specialized Research Fund for the Doctoral Program of Higher Education of China [20110042110017]
- Fundamental Research Funds for the Central Universities of China [N110105001, N120505001]
To explore the size effect on the mechanical properties of the coarse-grained materials and the relevant influence of sub-structures, the coarse-grained pure aluminum sheets with the thickness spanning from 0.2 to 2.0 mm are selected as experimental materials, on which the pre-fatigue deformation (pre-cycle is equal to 5% of fatigue life N-f) is exerted to alter internal sub-structures. The results show that the uniform strain epsilon of the annealed sheets almost linearly decreases with the reduction of thickness, and the ultimate tensile strength sigma(UTS) first slowly declines, then quickly drops as the thickness is below 0.5 mm, but the yield strength sigma(YS) does not exhibit an obvious thickness effect. The pre-fatigue deformation not only significantly improves the plasticity, but also decreases the critical thickness t(c) (below which the decrease in sigma(UTS) suddenly becomes notable) from 0.5 mm of the annealed state to 0.3 mm, meanwhile, a higher sigma(UTS) is maintained at the thickness ranging from 0.3 to 2.0 mm. For the annealed sheets, the cracks are initiated at grain boundaries (GBs), and with decreasing thickness, the appearance of a lot of straight slip lines leads to the occurrence of single slip separation failure in thinner sheets. The prefatigue deformation not only increases the uniform deformation degree in grain interiors, but also promotes the formation of more ill-developed cells in sub-grains and wall-cells and the development of the sub-grains in thinner sheets, so that all the pre-fatigued sheets exhibit ductile failure and a higher sigma(UTS) is obtained at the thickness between 0.3 and 1.0 mm. (c) 2014 Elsevier B.V. All rights reserved.
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