The Influence of Reinforcement Size on the Microstructure and Mechanical Behavior of a Nanostructured Aluminum-Based Metal Matrix Composite

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Behm, N. (2015). The Influence of Reinforcement Size on the Microstructure and Mechanical Behavior of a Nanostructured Aluminum-Based Metal Matrix Composite. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

With increased availability and growing commercial applications, aluminum- based metal matrix composites show promise as high specific strength structural materials. Before they can be implemented however, they require thorough characterization and testing. A novel nanostructured aluminum-based metal matrix composite (MMC) was characterized through a combination of microstructural analysis and mechanical testing. Two composites were studied, an aluminum MMC reinforced with 50 nm boron carbide, (B4C) and an aluminum MMC reinforced with 500 nm boron carbide. Transmission electron microscopy (TEM) analysis revealed an ultra-fine grained matrix with grains on the order of 100 – 300 nm. The quasi-static and dynamic response of the composites was compared with the behavior of the unreinforced aluminum alloy, and it was found that the reinforcement resulted in a 30% improvement in strength. The decrease in the reinforcement size from 500 to 50 nm activated an additional strengthening mechanism, which further improved the strength of the MMC reinforced with the 50 nm B4C. Dynamic compression tests were performed at elevated temperatures up 400 oC on the composites, and it was found that they exhibited impressive strengths considering the thermal softening prevalent in aluminum. The reinforcement size was found to play an important role in the strain softening exhibited at elevated temperature, fracture mechanism, and composite strength. Models to describe the composite behavior are presented.

Details
Author

Behm, Nathan

Title

The Influence of Reinforcement Size on the Microstructure and Mechanical Behavior of a Nanostructured Aluminum-Based Metal Matrix Composite

Physical Description

1 online resource (143 pages) : PDF

Date

2015

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

With increased availability and growing commercial applications, aluminum- based metal matrix composites show promise as high specific strength structural materials. Before they can be implemented however, they require thorough characterization and testing. A novel nanostructured aluminum-based metal matrix composite (MMC) was characterized through a combination of microstructural analysis and mechanical testing. Two composites were studied, an aluminum MMC reinforced with 50 nm boron carbide, (B4C) and an aluminum MMC reinforced with 500 nm boron carbide. Transmission electron microscopy (TEM) analysis revealed an ultra-fine grained matrix with grains on the order of 100 – 300 nm. The quasi-static and dynamic response of the composites was compared with the behavior of the unreinforced aluminum alloy, and it was found that the reinforcement resulted in a 30% improvement in strength. The decrease in the reinforcement size from 500 to 50 nm activated an additional strengthening mechanism, which further improved the strength of the MMC reinforced with the 50 nm B4C. Dynamic compression tests were performed at elevated temperatures up 400 oC on the composites, and it was found that they exhibited impressive strengths considering the thermal softening prevalent in aluminum. The reinforcement size was found to play an important role in the strain softening exhibited at elevated temperature, fracture mechanism, and composite strength. Models to describe the composite behavior are presented.

Genre

doctoral dissertations

Subjects--Topics

Mechanical engineering
Materials science
Nanoscience

Degree

Ph.D.

Keywords

Adiabatic Shear Bands
High Strain Rate
Metal Matrix Composites
Microstructure
Nanoscale

Subject Area

Nanoscale Science

Advisor(s)

Wei, Qiuming

Committee Members

Zhang, Haitao
Cherukuri, Harish
Smelser, Ronald
Chen, Don

Degree Note

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2015.

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Rights Holder Information

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Identifier

Behm_uncc_0694D_10968

Permalink

http://hdl.handle.net/20.500.13093/etd:869