Modification of the eutectic silicon in Al-Si alloys is traditionally performed by sodium and strontium addition. Although not traditionally used as a modifier, calcium also has the potential to modify the eutectic silicon in Al-Si alloys. Metallographic observation and thermal analysis studies in A357 alloy indicate that. when the cooling rate is quite low. Ca modifies the eutectic silicon. but the effect of Ca as a modifier is not as strong as is Na or Sr. When the cooling rate is high, a fully modified structure can be obtained with calcium. Recovery of Ca in the melt is high and certain. It does not fade with long holding times. Moreover, a premodified ingot can be used, and even when such all ingot is remelted repeatedly there is no calcium loss. / Calcium does increase porosity in castings. In general modification treatment with Ca improves mechanical properties, especially elongation. / Calcium adversely interacts with strontium and reduces the ability of strontium as a modifier. Microstructural and thermal analysis studies show that Ca has a deleterious effect on Sr-modified castings and vice versa. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.20492 |
| Date | January 1998 |
| Creators | Abdollahi, Ahmad. |
| 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 | Master of Engineering (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001610272, proquestno: MQ43991, Theses scanned by UMI/ProQuest. |
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