期刊
MATERIALS & DESIGN
卷 125, 期 -, 页码 116-125出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.matdes.2017.03.081
关键词
Aluminum alloys; Multi-pass friction stir processing; Mechanical anisotropy; Grain boundary sliding; High strain rate superplasticity; Small punch test
资金
- MINECO [MAT2012-38962, MAT2015-68919-R, BES-2013-063963]
- CSIC
- European Social Fund FSE
Multi-pass friction stir processing (MP-FSP) can produce extensive bulk nanostructured areas in various metallic materials, such as the Al 7075 alloy (Al-Zn-Mg-Cu), providing fine and highly misoriented grains. This allows obtaining superplastic deformations by the activation of grain boundary sliding (GBS) mechanism at certain strain rate and temperature window, crucial for performing a further superplastic forming (SPF). The superplastic performance of theMP-FSP Al 7075 alloy in two uniaxial testing directions was evaluated and compared to that of a single pass FSP (SP-FSP), reporting a mechanical anisotropy in the MP-FSP attributed to the heterogeneous crystallographic orientation distribution along the transverse testing direction. The operative deformation mechanism was determined by uniaxial tensile test and small punch test (SPT), the former a test with biaxial with radial symmetry. GBS was corroborated as the main operative deformation mechanism in the SP-FSP and MP-FSP, reporting high strain rate superplasticity in the temperature range 350-400 degrees C at 10(-2) s(-1), and maximum elongation values between 290-540% at 400 degrees C depending on the testing direction. The Al 7075 alloy processed by MP-FSP showed a great potential for a further SPF as GBS remains as the global deformation mechanism under biaxial testing conditions. (C) 2017 Elsevier Ltd. All rights reserved.
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