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 ð MMC  Present research ð nanomaterial ð Spray (Aerosol) method ð Colliding drops

3. 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)

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 10 6 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, 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)

6. 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

7. 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.

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

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

14. 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

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 Microstructure of particle in 150-106  m size range. The ASTM grain size of this microstructure is approximately 10 25.4  m Magnification 1000X

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

18. 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.

19. 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%.

20. 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.

21. THANK YOU