| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 87 === The essential purpose of this research has been to investigate the effect of aging precipitate of oxide addition in 2014 Al alloy. 2014 pre-alloy powder were formed by CIP and liquid-sintered in H2 and air. It added oxygen content by means of different sintered atmosphere. Besides, the sample sintered in H2 had higher density and lower oxygen content than sintered in air.
There is different oxygen content in two samples sintered in H2 and air in OM and SEM. There is more oxide in the sample sintered in air. The analyses of EPMA and EDAX showed equilibrium phase θ was uniformly distributed in the matrix, and precipitates was clustered where is higher oxygen content in.
It obviously showed that existence of oxide changed the precipitated kinetics of 2014 Al alloys by DSC curves. Furthermore, major-hardening phases would delay due to introduction of oxide. In athermal aging curves, It showed that peak-aging of sample sintered in air would accelerated reach owing to existence of more oxide.
It showed under TEM, when increasing aging time, the sequence of sample sintered in H2 is in accordance with normal precipitated behavior. The sequence is: αs.s→α＋G.P.Zone→α＋λ￠→α＋λ￠＋θ￠→α＋λ＋θ. On the other hand, in the situation of the sample sintered in air, it observed a great quantity equilibrium phase θ nucleated on interfaces between oxide and matrix. Owing to pre-precipitated phaseθdepleted solute atoms in the matrix., it would cause major hardening phaseθ￠ precipitate hardly. It was also one of the reason why mechanical properties of 2014 Al alloys became worse.
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