1. Phase transformation by mechanical milling Partha Protim Chattopadhyay

2. Contents Energy flow in materials
Mechanically driven phase transformation
Experimental techniques for mechanically driven phase transformation
Mechanical milling
Grain refinement by mechanical milling
Different types of phase transformation by mechanical milling
Some practical examples of mechanically driven phase transformation

3. Temperature Stress/Strain Energy flow in engineering materials1
Temperature Stress/Strain 2
Microstructure
Energy flow in engineering materials
1. Thermal Stress
2. Heat generation due to mechanical work
3. Temperature dependent phase transformation
4. Latent heat
5. Transformation dilation
6. Stress induced phase transformation

4. Mechanically driven microstructural evolution
Deformation localization in shear bands containing a high dislocation density
Annihilation/recombination/rearrangement of dislocation to form cell/subgrain structure with finer dimension
Random orientation of grains, i.e., low angle grain boundary  high angle grain boundary  grain boundary sliding rotation

5. Experimental techniques for Mechanically driven phase transformation
Angular torsion
Equal channel angular extrusion
Pack rolling
Mechanical milling

6. Grain refinement by mechanical milling
Microstructure formation by ball milling
Mechanics of a planetary ball mill
Microcrystalline structure
Nanocrystalline structure

7. Effect of grain refinement in polycrystalline materials

10. Polymorphic transformation in Nb
Calculated lattice expansion in  3.7%
Measured lattice expansion  4%
Calculated stored energy 4.35 x 10-20J/atom
Earlier reported value 1.46 x 10-20J/atom

12. Defect induced disordering of the crystalline alloys
Amorphisation by Mechanical Milling
Pioneered by Koch et al. in the case of Nb-Ni system
Most widely studied SSA technique
Achieved in the mixture of pure metal, intermetallics etc
Defect induced disordering of the crystalline alloys
Repetitive cold welding and fracture
Alloying
Amorphization

13. Complete amorphization in Al65Cu20(TM)15

14. Machining/wear

15. Phase transformation in wear resistance coating material by mechanical milling

16. Mechanical milling of Al and 316 stainless steel
25 wt% Al
65 wt% Al
85 wt% Al
65 % El.SS

17. THANK YOU