Kelley, Brian Thomas
(2025)
The Impact of Increased Recycle Content on Microstructure, Tensile Properties and Hemming Capability in Automotive Al-Mg-Si Alloys.
Master's Thesis, University of Pittsburgh.
(Unpublished)
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Abstract
The following study investigated the impact of increased aluminum scrap utilization on the microstructure and mechanical properties of Al-Mg-Si alloys for use in automotive applications. Scrap-tolerant alloys represent a key developmental area as the automotive industry continues to strive for greater sustainability and lower cost. For the purposes of this study, a hypothetical scrap mixture, based on a projection from Ford F-150 post-consumer 6XXX (Al-Mg-Si) scrap, was used to derive three alloy compositions of interest. Each alloy targeted a base composition of Mg, Si, and Cu designed to meet Ford WSS-A175-A2 specification requirements, which is a grade commonly used in exposed applications requiring improved local formability for door hem operations. The three alloys targeted 0%, 33%, and 67% recycle content with Fe and Mn increasing as recycle content increased. To determine the impact of thermo-mechanical processing on the scrap tolerance of these alloys, each alloy was rolled to a final gauge of 1.0 mm, targeting cold reductions of 70%, 80% and 90%. Additionally, each alloy was heat treated using two separate practices, with the first targeting near the center of the Ford yield strength specification limits and the second targeting full dissolution of Mg2Si.
Alloy microstructure was evaluated using optical metallography and scanning electron microscopy to identify and quantify observed phases. Additionally, electron backscatter diffraction was used to measure grain size. Tensile testing with measurement of plastic strain ratio was used to evaluate mechanical properties associated with global formability. VDA bend testing and Ford flat hem testing was used to evaluate hemming capability.
Overall, this study found that moderate levels of scrap could be used to improve overall performance with appropriate thermomechanical processing modifications, as the local formability can be improved with increasing cold work without significant, negative impacts to tensile properties. However, higher levels of scrap were found to be exceedingly detrimental to global formability properties, likely hindering their general use for automotive applications. Future work is suggested to better understand how recycle content affects texture evolution during thermomechanical processing as such information could be leveraged to further refine processing strategies to increase the amount of allowable recycling content.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
| Creators | Email | Pitt Username | ORCID  |
|---|
| Kelley, Brian Thomas | btk38@pitt.edu | btk38 | |
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| ETD Committee: |
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| Date: |
7 January 2025 |
| Date Type: |
Publication |
| Defense Date: |
14 November 2024 |
| Approval Date: |
7 January 2025 |
| Submission Date: |
5 November 2024 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
82 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Materials Science and Engineering |
| Degree: |
MS - Master of Science |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
N/A |
| Date Deposited: |
07 Jan 2025 21:05 |
| Last Modified: |
07 Jan 2025 21:05 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/47039 |
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