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Explore the innovative methods of powder production through atomization and chemical reactions for manufacturing metal matrix composites. Discover the properties, production methods, and experimental apparatus involved in this cutting-edge research field at the University of Toronto.
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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
Outline • Overview of the previous work • MMC • Present research • nanomaterial • Spray (Aerosol) method • Colliding drops
MMC Properties Compared to Matrix Material: Metal Matrix Composite Powder • 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 Ceramic Particles (high toughness, strength, machinability) (high strength, stiffness & thermal stability)
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 106 metric tons/year. Annual market size of metal powder is $3 billion and corresponding P/M size is $6 billion.
MMC • Matrix: Al, Ti, Ni, Steel • Particles: SiC, TiC, Al2O3, SiN4, Si • Difficult to incorporate due to non-wetting (>90o) behavior • Undesirable interfacial reaction at high T (brittle interfacial phase)
Methods of MMC Production 1. Atomization of Premixed MMC • SiC particles mixed into molten aluminum alloy; • Without stirring SiC particles settle (Al = 2400 kg/m3 and SiC = 3200 kg/m3); • Brittle interfacial reactions occur due to long resident times
Vz(r,z) V(r,z) Vr(r,z) (r) R Rotating Disk Atomization • 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.
Controlling Parameters • RPM • Feed Rate • Disk Design • Liquid Metal Properties Atomization Modes • Direct Drop Mode; • Ligament Mode; • Sheet Formation Mode.
Centrifugal Atomization With Particle Injection Disk • Minimized interfacial interaction; • Limited reinforcement segregation; • Rapidly solidified microstructure.
Tank X-Y Controls
Crucible and Furnace Motor for Raising Rod Connection for Argon SS Plate Gasket Bolt Crucible Bottom of Rod 6061 Aluminum alloy chosen as matrix
Air Motor And Disk • Disk preheated to 750 oC 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. Heating Light Disk Nozzle Air Motor
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
ASTM 112 - 95 Grain Size Magnification 1000X 25.4 m Microstructure of particle in 150-106 m size range. The ASTM grain size of this microstructure is approximately 10
SiC Volume Fraction in Composite Powder SiC Particle Average: SiC 18% Vol. Void 1.2% Vol. Void Aluminum Particle
SiC Volume Fraction in Composite Powder Significant Particle Penetration. SiC Particle Magnification 1000X 25.4 m Microstructure of particle in 150-125 mm 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 Volume Fraction in Composite Powder Magnification 1000X 25.4 m Microstructure of particle in 90-106 mm 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%.
Conclusions • A new method of MMC powder production is developed; • SiCp are successfully injected into the Al matrix. (18% vol SiC) • MMC particles are not spherical; • Mainly, ligaments, teardrops & tad poles. • Oxidation believed to be the main cause.