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Development of hypereutectic Al-Si based P/M alloys

Su, Shei Sia (2012)
Ph.D. thesis, University of Birmingham.

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Abstract

The compaction, sintering and heat treatment processing conditions for the commercial powder, Ecka Alumix 231 with the nominal composition of Al-15Si-2.5Cu-0.5Mg(wt%) have been optimized in this study. It has been found that
densification of Ecka Alumix 231 depended largely on the sintering atmosphere and the amount of liquid phase presented. Sintering in nitrogen atmosphere was found to be beneficial due to the formation of AIN which later induced pore filling effect. Presence of hydrogen in the sintering atmosphere, however, was not desirable. Decomposition of MgH2 at higher temperature was suggested to increase the pore pressure and caused detrimental effect on compact
densification.

The effects of alloy additions (i.e. Cu and/or Ni) on sintering and heat treatment response were also investigated in this study. Addition of copper was found to
enhance the sintering response by a significant increase in the sintered density,reduced the peak ageing temperatures and time. Nickel addition, however, was detrimental to both sintering and heat treatment response since it reduced the
amount of copper content dissolved in the α-aluminum due to the formation of Al\(_3\)(Ni,Cu)\(_2\) phase. The precipitation sequence for Al-Si-Cu-Mg-(Ni) was suggested to be: Supersaturated solid solution (SSS)→GP zones → θ” → θ’ → θ.

Type of Work:Ph.D. thesis.
Supervisor(s):Chang, I. T. H.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:3538
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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