In-situ synthesis of aluminum nitride+ magnesium silicide/Magnesium matrix composites and microstructral studies
Abstract
Magnesium matrix composites with AlN and Mg2Si reinforcement are potential engineering materials for automobile and aerospace applications. Fine particulate AlN/Mg composites have been successfully in-situ synthesized using Mg alloy and Al shots and Si3N4 powder as raw materials. Reaction under argon atmosphere or SF6/CO2 protective gas atmosphere at 770 to 850°C for an hour was used to produce composites containing different volume fraction of AlN (+ residual Mg 2Si) depending on the reaction temperature. The microstructures were characterized using X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy. Fine AlN particles embedded within magnesium matrix in addition to a larger size Mg2Si phase was observed after the in-situ reaction. The AlN particles were found to have formed from the prior Si3N4 agglomerates while the morphology of the Mg2Si phase was dependent upon the composition, temperature and cooling rate. Thermodynamic calculations including the equilibrium and Scheil solidification paths of the resultant alloy after the in situ reaction were performed and compared. At the same time, reaction mechanism was studied using SEM and TEM and a “core-shell” reaction mechanism was supported.
Degree
M.S.M.S.E.
Advisors
Johnson, Purdue University.
Subject Area
Materials science
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