A brief introduction to solid state phase transformation

1. Introduction to solid state
phase transformation
R.Arul Vigneswar
7/12/2013 Summer intern seminar 1

2. Phase
• “Physically distinct, chemically homogeneous and mechanically
separable part of a system”
• Involves
I. State of aggregation
II. Composition
III. Crystal structure
IV. Electronic structure
7/12/2013 Summer intern seminar 2

3. Atom movements
• Movements over
a. A large number of interatomic distance (ex. Long range diffusion)
b. One or two interatomic distance (ex. Short range diffusion)
c. Fraction of interatomic distance (ex. Diffusionless changes)
7/12/2013 Summer intern seminar 3

4. Types
• Change in composition
7/12/2013 Summer intern seminar 4
α α1 + α2
FCC FCC FCC
39.5 21 56
Structure
Zn,at.%

5. • Change in crystal structure
7/12/2013 Summer intern seminar 5
δ Fe γ Fe α Fe1392°C 911°C
Structure BCC FCC BCC

6. • Compositional and crystal structure changes
7/12/2013 Summer intern seminar 6
α supersat α sat + θ
Structure FCC FCC BCT
Cu,wt.% 4.5 0.3 52
Austenite Ferrite + Cementite
FCC BCC Orthorhombic
0.8 0.02 6.69
Structure
C,wt.%

7. • Change in order
7/12/2013 Summer intern seminar 7

8. • Electronic transitions
I. Curie temperature in Iron (769°C)
II. Neel temperature in MnO (-157°C)
7/12/2013 Summer intern seminar 8

9. Homogeneous and heterogeneous
transformations
• Homogeneous transformation- takes place simultaneously in all parts
• Heterogeneous transformation- nucleation and growth type
7/12/2013 Summer intern seminar 9

10. Reference
7/12/2013 Summer intern seminar 10