Powder Production through Atomization & Chemical Reactions

1. Powder Production through Atomization & Chemical Reactions N. Ashgriz Centre for Advanced Coating Technologies Department of Mechanical & Industrial Engineering University of Toronto

2. Outline • Overview of the previous work • MMC • Present research • nanomaterial • Spray (Aerosol) method • Colliding drops

3. 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)

4. 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.

5. 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)

6. 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

7. 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.

8. Controlling Parameters • RPM • Feed Rate • Disk Design • Liquid Metal Properties Atomization Modes • Direct Drop Mode; • Ligament Mode; • Sheet Formation Mode.

9. Ligament Formation

10. Centrifugal Atomization With Particle Injection Disk • Minimized interfacial interaction; • Limited reinforcement segregation; • Rapidly solidified microstructure.

11. Experimental Apparatus

12. Tank X-Y Controls

13. Crucible and Furnace Motor for Raising Rod Connection for Argon SS Plate Gasket Bolt Crucible Bottom of Rod 6061 Aluminum alloy chosen as matrix

14. 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

15. 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

16. 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

17. SiC Volume Fraction in Composite Powder SiC Particle Average: SiC 18% Vol. Void 1.2% Vol. Void Aluminum Particle

18. 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%.

19. 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%.

20. 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.

21. THANK YOU