1. Micro-Hardness Characteristics and Morphology of Cr-Coating formed due to Mechanical Alloying A. Bakhshai, G.S. Dengler, and A.R.Torosyan Department of Physics, Goucher College, Baltimore, Maryland 21204

2. What is Ball Milling?

3. How Does the Reaction Propogate? Increase in Surface to Volume Ratio Increase in Heat as a result of the Kinetic energy of the milling balls Cold Welding of the Powder to substrate

4. Key Variables Milling Time Number and Size of Milling Balls Powder Mass Powder Mass to Ball Ratio

5. Initial Experimental Problems Downward Curvature of the Substrate pressure gradient Solution: Insertion of a small hole in substrate prior to milling

6. Obtaining A Uniform Coating  Ring Formation  Uniformly coated substrate

7. Atomic Force Microscopy:Uniform Cr coating on Steel

8. Atomic Force Microscopy: Non- uniformity of the Cr-on-steel Sample

9. Effect of Mass of Cr Powder on Steel Substrate

10. Milling Time: Effects on Surface Morphology

11. Heat Treatment

12. Further Investigations: Cr Coating on Al substrate Studied: Powder mass in relationship to microhardness Displayed increase in microhardness with increase in powder mass Produced same characteristic curve as steel substrate Atomic Force Microscopy also showed increases in surface morphology with increased powder mass

13. Physical Properties of the Coating Powder

14. Anomaly: Cu Coating on Al Substrate No noticeable coating obtained under equivalent reaction conditions Alcohol, Acetone, Silicon oxide were used in an effort to stimulate reaction Copper coating obtained by shortening of milling time to 2 minutes

15. Conclusion