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Published byHubert Stephens Modified over 9 years ago
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Powder Production through Atomization & Chemical Reactions N. Ashgriz Centre for Advanced Coating Technologies Department of Mechanical & Industrial Engineering University of Toronto
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Outline Overview of the previous work ð MMC Present research ð nanomaterial ð Spray (Aerosol) method ð Colliding drops
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MMC Properties Compared to Matrix Material: Up to a 20% Improvement in Yield Strength Lower Coefficient of Thermal Expansion Higher Modulus of Elasticity (50%) More Wear Resistant Low Fracture Toughness Poor Fatigue Properties Metal Matrix Composite Powder Metal Matrix Ceramic Particles (high toughness, strength, machinability) (high strength, stiffness & thermal stability)
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Powder Production Methods Atomization ( Over 60% by weight of all powders produced in North America. ) Mechanical crushing Chemical reduction Vapor condensation Electrolytic method World wide Atomization capacity is 10 6 metric tons/year. Annual market size of metal powder is $3 billion and corresponding P/M size is $6 billion.
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MMC Matrix: Al, Ti, Ni, Steel Particles: SiC, TiC, Al 2 O 3, SiN 4, Si Difficult to incorporate due to non-wetting ( >90 o ) behavior Undesirable interfacial reaction at high T (brittle interfacial phase)
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Methods of MMC Production 1. Atomization of Premixed MMC ð SiC particles mixed into molten aluminum alloy; ð Without stirring SiC particles settle ( Al = 2400 kg/m 3 and SiC = 3200 kg/m 3 ); ð Brittle interfacial reactions occur due to long resident times
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Rotating Disk Atomization R (r) V r (r,z) V (r,z) V z (r,z) Highest atomization energy efficiency. Better control of the breakup process. Sever stresses due to high RPM. Thermal shock due to sudden impingement of the melt.
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Controlling Parameters Direct Drop Mode; Ligament Mode; Sheet Formation Mode. RPM Feed Rate Disk Design Liquid Metal Properties Atomization Modes
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Ligament Formation
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Centrifugal Atomization With Particle Injection Disk Minimized interfacial interaction; Limited reinforcement segregation; Rapidly solidified microstructure.
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Experimental Apparatus
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Tank X-Y Controls
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Crucible and Furnace Bottom of Rod Bolt SS Plate Connection for Argon Crucible Gasket Motor for Raising Rod 6061 Aluminum alloy chosen as matrix
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Air Motor And Disk Disk preheated to 750 o C with 4000 Watt light A pneumatic die grinder was used to rotate the 3 inch diameter disk. Disk speed:24,000 RPM. Disk is centered with X-Y table during experiment. Air Motor Disk Heating Light Nozzle
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Rotating Disk Atomization in He N=45000RPM m=0.2kg/s Cupper alloy: Cu-1% Cr - 0.6%Zr Titanium Alloy: Ti- 15%Mo -2.7%Nb – 3%Al - 0.2%Si
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ASTM 112 - 95 Grain Size Microstructure of particle in 150-106 m size range. The ASTM grain size of this microstructure is approximately 10 25.4 m Magnification 1000X
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SiC Particle Void Aluminum Particle SiC Volume Fraction in Composite Powder Average: SiC 18% Vol. Void 1.2% Vol.
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SiC Volume Fraction in Composite Powder Magnification 1000X Microstructure of particle in 150-125 m size range. The ASTM grain size is 11.9. The area of SiC particles is 11.1%. The area fraction of the void is 0.3%. SiC Particle 25.4 m Significant Particle Penetration.
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SiC Volume Fraction in Composite Powder Magnification 1000X 25.4 m Microstructure of particle in 90-106 m size range. The ASTM grain size is 10.6. The area of SiC particles is 13.3%. The area fraction of the void is 0.6%.
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Conclusions A new method of MMC powder production is developed; SiC p are successfully injected into the Al matrix. (18% vol SiC) MMC particles are not spherical; ð Mainly, ligaments, teardrops & tad poles. ð Oxidation believed to be the main cause.
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