Abstract

Metal matrix composite (N[MC) materials were manufactured using powder metallurgy (PM) techniques. Pure aluminum, Al, powder of mean particle size of 51 pm and alumina, AhO3, powder of 4 pm particle size were used as matrix and reinforcement, respectively. MNICs with four different weight fractions of reinforcement (e.g; Al-0wt.% AhO3, AI-2.5wt.% AhO3, Al-5wt.% AI2O3, and Al-1 0wt. %AhO3 ) were investigated The specimens were manufactured using hot compaction followed hot extrusion. Based on a preliminary study and on data published in the literature, two sets of processing parameters, designated as Scheme I and Scheme II, were used. The processing parameters for Scheme I consisted of: a compaction pressure of 74 :MPa, and temperature of 540 °C applied for 4 hours. In Scheme II, a compaction pressure of 157 l\.1Pa was used at a temperature of 600 °C applied for 3 hours. Mechanical behavior of the materials of both Schemes were studied using tension tests, microstructural examinations, and scanning electron micrographs (SEM) for fracture surface characterization. The effect of temperature of the deformation

behavior of Scheme II materials were examined by testing them at room temperature, 200 °C, 250 °C, and 300 °C. In Scheme I, the Al-Ah03 composites tested in tension at room temperature exhibited improvements in the yield strengths compared to the unreinforced Al matrix. However, the ultimate strengths were slightly lower in the composites than the unreinforced Al. Ductility of the materials tested in tension were almost identical( about 29 %) with slight reduction in the Al-2.5 wt.% Ah03, and Al-5 wt.% Ah03 composites. In Scheme II materials, the yield strengths of the Al-2.5% Al2O3 and Al-5% Ah03 composites improved 25% each whereas in the Al-10% A12O3 the strength improved up to 48%. A similar trend of improvement was also seen in the ultimate tensile strength of the composites with respect to the unreinforced matrix. High temperature tensile tests showed higher yield and tensile strengths but as the testing temperature exceeded 250 °C the composites exhibited lower mechanical properties compared to the unreinforced Al. Ductility of the unreinforced Al tested at 200 °C and 250 °C increased 10 % and 63 % over that of room temperature. However, as the testing temperature rose to 300 °C the ductility decreased 23% below that of 250 °C. In the A1-Ah03 composites, the ductility decreased as the testing temperature increased. Microstructural features of both schemes demonstrated the formation of small­ sized grains ( and sub grain structures) which decreased in size as the weight fraction of the reinforcing particles, Al203, increased and increased as the testing temperature increased. Scanning electron micrographs exhibited a ductile fracture mode where high population of dimples dominated the fracture surfaces. All results of both Schemes were discussed and analyzed based on an up-to-date literature search and in comparison with similar composites produced and investigated by different outside authors.

School

School of Sciences and Engineering

Date of Award

2-1-1998

Online Submission Date

1-1-1997

First Advisor

Asaad Mazen

Committee Member 1

Nahed Ahmed Abdelrahman

Committee Member 2

Mahmoud Farag

Committee Member 3

Maher Y.A. Younan

Document Type

Thesis

Extent

203 leaves

Library of Congress Subject Heading 1

Powder metallurgy

Rights

The American University in Cairo grants authors of theses and dissertations a maximum embargo period of two years from the date of submission, upon request. After the embargo elapses, these documents are made available publicly. If you are the author of this thesis or dissertation, and would like to request an exceptional extension of the embargo period, please write to thesisadmin@aucegypt.edu

Call Number

Thesis 1997/59

Location

mgfth

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