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Severe plastic deformation (SPD) has been known for decades to provide microstructural refinement under a hydrostatic stress state by introducing a tremendous quantity of lattice defects, including vacancies, dislocations, and grain boundaries, leading to enhanced mechanical properties. Many SPD processes have been well studied and utilized for the processing of ultrafine-grained (UFG) metals and materials. One major challenge with SPD-processed UFG materials is their limited applicability, primarily due to their microstructural stability at elevated temperatures and the difficulty of scaling up to larger sizes or volumes. To first understand the thermal stability of UFG material, a copper prepared by high-pressure torsion, a technique that can achieve true nano-scale grains in bulk samples, was evaluated using two novel in situ techniques of micro-beam high-energy synchrotron X-ray diffraction. These are, namely, monochromatic X-ray beams that yield changes in microstructure with time and temperature, and a polychromatic X-ray beam that determines grain reorientation behavior during microstructural relaxation. Furthermore, a new processing technique named cold angular rolling process (CARP) demonstrated some promise as an SPD technique for producing theoretically unlimited lengths of strength-enhanced copper sheets at room temperature with a relatively low energy consumption. Additional miniature tensile testing incorporating digital image correlation (DIC) method and microstructural analysis utilizing high-energy X-ray diffraction determined the influence of CARP having higher shear strain hardening in comparison with other established techniques. This study highlights the significance of lattice-defect influenced mechanical properties and microstructure of UFG obtained across multi-length scales and volumes, which are critical for guiding the control and scalable production of advanced materials for commercialization.
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The Cold Angular Rolling Process of Copper Sheets: Unraveling Plastic Deformation Behavior and Unveiling Microstructural Transformations
The cold angular rolling process (CARP) is being developed as a continuous severe plastic deformation technique, which can process metal sheets without any length limitations at room temperature. CARP contains cold rolling and equal‐channel angular process components. The sheet thickness is kept consistent before and after CARP, allowing multiple passes of the sheet. The desired microstructure and mechanical properties can be achieved in the processed metallic sheets. The current study is aimed to evaluate the capability of CARP by processing copper sheets with different sheet widths for repetitive passes. The CARP‐treated sheets are examined by lab‐scale X‐ray and high‐energy synchrotron X‐ray diffraction to investigate the evolution in dislocation density, texture, and strain anisotropy, and by tensile testing to identify the bulk mechanical properties. The digital image correlation method is applied to tensile testing so that strain localization within the sample gauge is visualized and deformation behavior is evaluated after yielding till postnecking by estimating the hardening exponent and strain hardening rate of the CARP‐treated sheet. Comparing the reported continuous and multiple‐step processes on Cu and its alloys, the present study confirms that the CARP is potentially a useful sheet process for strengthening ductile metals.
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- Award ID(s):
- 2051205
- PAR ID:
- 10457857
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Engineering Materials
- Volume:
- 26
- Issue:
- 4
- ISSN:
- 1438-1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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