Interplay Between Plastic Deformations and Optical Properites of Metal Surfaces: A Multiscale Study
The design of metallic surfaces with required surface quality and visual appearance represents a significant challenge for scientists and engineers. For example, the surface of aluminum products such as reflector bright sheet, aerospace structural components, and architectural materials is always required to have an attractive appearance under different lighting conditions and to be free of defects and corrosion [ref. 1]. Industrial-scale modification processes of metal alloy products (heat treatment, rolling, stretching, extruding, etc.) are closely related to different plastic phenomena. Although plastic deformation takes place at the macroscopic level, it significantly changes the surface geometry at the meso- and microscopic scales which may result in spectacular modifications of visual appearance of the deformed surface. Here we use a combination of confocal optical microscopy, orientation imaging microscopy with electron back scattering diffraction (EBSD), original morphological image analysis approach developed by the authors, and finite element simulations, in order to investigate the interplay of different plastic instabilities emerging in the course of plastic deformation, and visual appearance. It is demonstrated that visual brightness of aluminum sheet products could be significantly suppressed by some widely used industrial processes such as uniaxial stretching of the sheet. On the other hand, a properly designed “texture rolling” (i.e., embossing additional controlled engineered features into the metal surface) makes it significantly brighter than a conventionally rolled surface because these features may serve as sinks for otherwise incompatible plastic deformations and enhance brightness due to the suppression of roughness. It is expected that such “imaging transitions” are of general nature and could be observed for different metals and alloys exhibiting plastic instabilities. In turn, these results provide guidelines for the control of metal surface morphology in order to achieve desirable visual appearance, such as visual brightness and omnidirectional coloration.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC07-05ID14517
- OSTI ID:
- 978876
- Report Number(s):
- INL/JOU-09-16051; APPLAB; TRN: US201010%%254
- Journal Information:
- Applied Physics Letters, Vol. 95, Issue 8; ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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