The effect of grain size and temperature on the superplastic deformation behavior of a 7075 Al alloy
SCIE
SCOPUS
- Title
- The effect of grain size and temperature on the superplastic deformation behavior of a 7075 Al alloy
- Authors
- Kwon, YN; Chang, YW
- Date Issued
- 1999-08
- Publisher
- MINERALS METALS MATERIALS SOC
- Abstract
- The high-temperature deformation behavior of a 7075 Al alloy has been investigated within the framework of a recently proposed internal-variable theory for structural superplasticity (SSP). The flow curves were obtained by performing a series of load relaxation tests for specimens with various grain sizes, at temperatures ranging from 445 degrees C to 515 degrees C. The overall flow curves were then separated into two parts, according to the respective physical mechanisms, viz., the grain-boundary sliding (GBS) and the accommodating dislocation glide processes, contrary to the conventional approach which uses a single power-law relation. These individual curves were then analyzed based on the internal-variable theory. Much valuable information has been obtained in this way, providing new physical insight as well as a more comprehensive understanding of SSP. The GBS curve could be described as a Newtonian viscous flow, signified by the power-index value of M-g = 1.0 for this alloy. The unresolved issue of threshold stress is also clarified and identified as a critical stress required for the GBS. The role of grain refinement is found to shift the gain-matrix deformation (GMD) curve into a higher stress and strain-rate region, while the GBS curve into a lower stress and higher strain-rate region along the respective characteristic scaling line to bring both curves into a common flow-stress region, in which the GMD and GBS can operate simultaneously, resulting in the usual superplastic deformation behavior.
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/11431
- DOI
- 10.1007/s11661-999-0014-z
- ISSN
- 1073-5623
- Article Type
- Article
- Citation
- METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, vol. 30, no. 8, page. 2037 - 2047, 1999-08
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