Previous studies on Al85Yx Ni15-x glasses established a correlation between crystallization mode (pure growth versus nucleation and growth) and crystallization product. Glasses with approximate compositions x = 5, 7, 8, 10 were studied in order to accurately ascertain the nature of the structural variance which gives rise to different crystallization modes and the identity of the resulting crystallization products. Glasses with x = 5, 10 have a clear distinction: x = 5 contains quenched-in Al nanocrystals which act as nucleating centers leading to alpha-Al as the first crystalline product; equilibrium crystalline phases are alpha-Al, Al3Ni and a stacking variation of Al4YNi. x = 10 is a homogeneous glass which undergoes a glass transition prior to crystallization; first crystalline product is an unstable FCC structure which breaks down via Al segregation; equilibrium phases are alpha-Al, beta-Al3Y and Al16YNi 3. x = 7,8 share these characteristics: x = 7 contains quenched-in Al-nanocrystals and follows the initial x = 5 pattern of primary Al crystallization; however it undergoes a glass transition prior to first stage crystallization and equilibrium phases are alpha-Al, beta-Al3Y and Al16YNi3. x = 8 crystallizes by nucleation and growth yet has identical crystallization products as the corresponding x = 7 crystallization stages. Isothermal annealing prior to first two crystallization stages of x = 8 yields alpha-Al and the unstable FCC structure. Isothermal crystallization is complex, frequently involving the overlap of multiply nucleating phases and the sequential nucleation of successive crystallization stages at the same annealing temperature. The results of these crystallization studies imply that Al-Y-Ni glasses obey the cluster model (Al-Y versus Al-Ni clusters) where cluster-cluster correlation establishes the degree of medium-range order and presence or absence of Al nanocrystals. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.20284 |
| Date | January 1997 |
| Creators | Saini, Sajan. |
| Contributors | Altounian, Z. (advisor) |
| 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 Science (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001609795, proquestno: MQ44269, Theses scanned by UMI/ProQuest. |
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