Miranda, Ryan
(2023)
Effect of Vanadium Additions on Dispersoid Formation and Performance of AA6111.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
This study presents and investigates the effect of processing variations and alloy additions on the 6xxx series aluminum automotive alloy AA6111. 6xxx series aluminum alloys play an integral role in the automotive industry. Current developments are centered around maintaining high strength while improving bendability and crash performance. AA6111 contains intentional additions of manganese and unintentional additions of chromium which help control the grain structure by forming a population of fine dispersoid particles during high temperature homogenization. These dispersoid particles act as grain boundary pinning particles during recrystallization, which occurs during final solution heat treatment. It is also theorized that these fine dispersoid particles also more evenly distribute strain during deformation, improving formability. Vanadium, like manganese and chromium, will also form dispersoid particles in aluminum. This study aimed to evaluate how modifications to high temperature homogenization time and vanadium additions affect the microstructure and resulting properties of AA6111.
Thermodynamic calculations were used to optimize the homogenization temperature and predict the amount of dispersoid formed during this treatment. Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Electron Backscatter Diffraction (EBSD) techniques were used to characterize and quantify the dispersoid particles and grain structures.
Optical microscopy was used to evaluate the various samples in the as-homogenized condition. After etching the samples, the etch pits give an initial indication of amount of dispersoids present even though this technique does not have high enough resolution to image the dispersoids themselves.
SEM images were randomly captured on all samples in the as-homogenized condition and used to calculate area fraction of dispersoid present. Vanadium additions led to an increased area fraction of dispersoids when given a 24-hour homogenization treatment. Additionally, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) identified vanadium in solid solution, in constituent particles, and in dispersoids.
EBSD measured the area-weighted grain size of the samples in the final T6 temper to assess the effect of homogenization time and cold work level on final grain size. In all conditions regardless of cold work, the vanadium additions were able to further reduce the grain size by 2 to 4 microns depending on the condition.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
13 June 2023 |
| Date Type: |
Publication |
| Defense Date: |
6 March 2023 |
| Approval Date: |
13 June 2023 |
| Submission Date: |
10 March 2023 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
66 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering and Materials Science |
| Degree: |
MS - Master of Science |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Automotive aluminum, vanadium, 6xxx series |
| Date Deposited: |
13 Jun 2023 14:07 |
| Last Modified: |
13 Jun 2023 14:07 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/44271 |
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