Al-7%Si-0.3Mg (A356) foundry alloy is strontium modified and heat treated in order to obtain optimum mechanical properties. To date, the role that strontium modification plays in the precipitation process during the heat treatment is not well understood. The objective of the present work is to obtain a better understanding of the effect that strontium modification and heat treatment parameters exert on the properties of heat-treated Al-7%Si-0.3Mg alloy. The investigation consisted of a systematic measurement of the electrical conductivity and matrix microhardness of heat-treated coupons under different process conditions. Tensile properties were also measured and a transmission electron microscopy study of critical samples was done. The results obtained in this work indicate that the heat treatment of this alloy can be optimized. Solution heat treatment and artificial aging can be reduced and natural aging manipulated. The use of a continuous heating artificial aging is proposed. During the heat treatment of the A356 alloy under certain conditions not only does the precipitation of the Mg2Si occur, but also that of silicon. It was found that strontium modification does not influence the precipitation kinetics of the Mg2Si, but it does retard the precipitation of the silicon out of the matrix.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.19547 |
| Date | January 2003 |
| Creators | Hernández Paz, Juan Francisco |
| 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 | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002021498, Theses scanned by McGill Library. |
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