期刊
ACTA MATERIALIA
卷 59, 期 13, 页码 5159-5170出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2011.04.051
关键词
Aluminium alloys; Superplasticity; Grain boundary diffusion; Shear test; Focused ion beams
资金
- University of Oxford
- National Science Foundation
The deformation mechanisms responsible for superplastic deformation have long remained a controversial subject. This research clarifies the issue by using regular surface grids with submicron and coarser pitches to make quantitative measurements of grain boundary sliding, diffusional transfer of material at grain boundaries and intragranular deformation during superplastic deformation in shear at the optimum superplastic strain rate. Important artefacts associated with surface oxidation and grain boundary migration were identified by removing surface material with a focused ion beam (FIB) to examine the microstructure beneath. The results show that Region II superplasticity occurs by diffusion creep with a grain neighbour switching geometry. Direct and incontrovertible experimental evidence of stress-directed diffusional transfer of matter at grain boundaries and of grain neighbour switching is described. There was no significant deformation within the grains by dislocation motion. The diffusional geometry was consistent with existing models for the process. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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