Liu, Yuzhe
(2024)
Microstructure Evolution In Al-(Cu,Ag) Alloy Thin Films During Pulsed Laser Induced Rapid Solidification.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Observing rapid transient processes during solidification has proved to be a challenge for conventional characterization techniques due to their inability to meet the required spatiotemporal resolution. However, recent advances in ultra-fast time-resolved in-situ transmission electron microscopy have enabled the characterization of pulsed laser-induced melting and rapid solidification processes in Al-(Cu,Ag) alloys with unprecedented spatiotemporal resolution using the unique Dynamic Transmission Electron Microscope (DTEM). The DTEM achieves its high spatiotemporal resolution by modifying a conventional TEM with two laser systems: the image formation laser system and process initiation laser system. This study utilized in-situ Movie-Mode Dynamic Transmission Electron Microscope (MM-DTEM) experimentation to document rapid solidification processes in Al-(Cu,Ag) alloy thin films. The use of machine learning techniques, in conjunction with post-mortem characterization tools, has unveiled a promising approach for comprehending morphological evolution during rapid solidification processes. Specifically, the binary analysis of STEM images, empowered by advanced machine learning algorithms, provides an in-depth look into the key metrics that describe these morphological transitions. This study enables accurate determination of average velocity of solidification evolution and associated crystal growth mode changes during rapid solidification process in hypo-eutectic (Cu concentration below 17.1 atomic percent) and hyper-eutectic (Cu concentration above 17.1 atomic percent) Al–Cu alloys and hypoeutectic Al-(Cu,Ag) alloy.
This interdisciplinary approach harnesses STEM's high-resolution capabilities and machine learning's computational prowess to extract nuanced details from complex solidification patterns. Furthermore, this intricate analysis is essential for underpinning the integrity and validity of computational models predicting rapid solidification behavior.
Moreover, the synergy of in-situ MM-DTEM observations with these post-mortem characterization techniques amplifies our capacity to derive quantitative markers. These markers are invaluable for understanding the fundamental behaviors of alloys during rapid solidification and ensuring the accuracy and precision of computational models.
This study offers a robust and comprehensive framework to validate and refine rapid solidification models, promising enhanced predictive accuracy and a deeper understanding of alloy behavior under rapid cooling conditions.
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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: |
11 January 2024 |
| Date Type: |
Publication |
| Defense Date: |
6 November 2023 |
| Approval Date: |
11 January 2024 |
| Submission Date: |
29 October 2023 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
195 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering and Materials Science |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Transmission Electron Microscopy, in Situ TEM, Rapid Solidification, Aluminum Copper Silver Alloy, Aluminum Copper Alloy, Laser |
| Date Deposited: |
11 Jan 2024 19:41 |
| Last Modified: |
11 Jan 2024 19:41 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/45476 |
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