Hot tearing is a common defect during DC casting of some commercial aluminum alloys and can result in considerable productivity loss in the cast-house. In order to better understand the hot tearing, a novel technique, dubbed DCSS for Direct Chill Surface Simulator, has been developed to reproduce the cooling conditions at the mould/liquid metal interface and to generate the unique surface and sub-surface microstructure of the DC ingot. The apparatus has been designed also to apply and measure a tensile load and the surface strain. These mechanical quantities were then used to derive the stress-strain curves that best represent the material behaviour during solidification and its capacity to resist hot tearing. / The present work describes the approach used to determine the mechanical resistance of three different aluminum-silicon binary alloys (AI-0.5wt%Si, Al-1.5wt%Si, and Al-2.5wt%Si). In addition, the present work covers the modeling of the heat transfer encountered during the test using commercial software (ProCAST(TM)) to better understand the temperature field upon solidification and tracking the solid fraction. Microstructure analyses were made to obtain various metallurgical quantities (e.g., grain morphology, size), physical measurements and thorough investigation of the torn surfaces. Information was used as inputs to the various models developed and used in the present work. / A theoretical model was updated from previous work using more realistic metallurgical quantities. This research led also to the development of a probalistic model (cellular automata) to simulate the microstructure of the cast sample. The model has been used to determine a crack propagation coefficient (CPC) that was used in the theoretical model to better represent the hot tear propagation. / Work to include even more complex coupled phenomena such as creep phenomena and microsegregation are not covered in the present scope of this work. Hypotheses are raised according to experimental work and observations made that suggest their most probable contributions. These studies have advanced to a certain degree the scientific understanding of hot tearing such as the inherent mechanical behaviour during solidification. In addition, the DCSS was used successfully to rank DC cast commercial wrought alloys in terms of hot tearing susceptibility.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102995 |
| Date | January 2006 |
| Creators | Langlais, Joseph. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining, Metals and Materials Engineering.) |
| Rights | © Joseph Langlais, 2006 |
| Relation | alephsysno: 002589590, proquestno: AAINR32205, Theses scanned by UMI/ProQuest. |
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