|Author's Email Address
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||Materials and Optoelectronic Science|
|Type of Document
||In situ synthesis of nanoparticles reinforced Al-based composites from Al-SiO2, Al-CuO and Al-Mg-CuO systems by friction stir processing|
|Date of Defense
Aluminum based composite
Friction stir process
In situ composite
||Aluminum matrix composites reinforced with nanometer-sized particles were produced from powder mixture of Al and oxides by using friction stir processing (FSP). This approach combined the hot working nature of FSP and exothermic reactions between Al and oxides. In this study, composites synthesized from Al-SiO2, Al-CuO and Al-Mg-CuO were investigated, and the microstructure and mechanical properties of the composites were characterized.|
In the Al-SiO2 composites, Al2O3 particles were produced in situ by oxide-aluminum displacement reactions. The Al2O3 particles were formed at the Al/SiO2 interface, and dispersed in the aluminum matrix by the stirring action of the rotating tool during FSP. Microstructural examinations revealed the Al2O3 particles present mainly in the form of clusters of nano-sized (approximately 20 nm) particles, which were identified as α-Al2O3. Because of the fine dispersion of nano-sized particles in an ultrafine-grained aluminum matrix, the composites exhibit superior tensile strength and ductility. Quantitative phase analysis indicated that the extent of the Al-SiO2 reaction increased in conjunction with an increasing tool rotation rate and a decreasing tool traverse speed in FSP.
In the Al-CuO composite, the in situ formed reinforcements include nanometer-sized Al2O3 and Al2Cu particles. These Al2O3 nano-particles were identified as amorphous in the as-FSPed condition. The average Al grain size in the FSPed composite was approximately 1 μm. The composite exhibited enhanced strength. The major contributions to the high strength of the composite are the ultrafine grained structure of aluminum matrix and the fine dispersion of nanometer-size reinforcing particles inside aluminum grains.
Aluminum based in situ composite was synthesized from powder mixture of Al/Mg/CuO by using friction stir processing (FSP). Microstructure characterization indicates that in situ formed MgO and Al2Cu nano-particles are uniformly distrubuted in submicron-grained aluminum matrix. Because of the large amount of nanometer-size reinforcements in a submicron-grained matrix, the composite exhibits superior Young’s modulus and strength. The reaction mechanism responsible for the in situ formation of MgO and Al2Cu particles in FSP is discussed. This work has demonstrated the beneficial effect of utilizing the Mg/metal-oxide displacement reaction in the synthesis of aluminum based in situ composite.
||New-Jin Ho - chair|
Chung-Yi Yu - co-chair
Liu-wen Chang - co-chair
Ker-Chang Hsieh - co-chair
Shuei-Yuan Chen - co-chair
Po-We Kao - advisor
Indicate in-campus at 3 year and off-campus access at 3 year.|
|Date of Submission