Question

Bain distortion model explains:

• A. The atomic movement involved in martensitic transformation
• B. Formation of bainite by isothermal transformation
• C. Formation of pearlite by eutectoid transformation
• D. Formation of ledeburite by eutectic transformation

Hint:

The Bain distortion model describes how FCC austenite transforms into BCT martensite without diffusion — via lattice distortion.

Answer 1

The Correct Option is A

Step 1: What is the Bain Distortion Model?
The Bain distortion model describes the mechanism of atomic movement during the transformation of austenite (FCC) to martensite (BCT) in steel. Step 2: Nature of Martensitic Transformation
- It is a diffusionless transformation, - Occurs by a coordinated shear-like movement of atoms, - Results in a rapid, hard, and brittle microstructure. Step 3: Bain's Proposal
Bain proposed that: - The FCC lattice of austenite contracts in one direction and expands in the other two directions, - This distortion transforms the structure into a body-centered tetragonal (BCT) lattice, representing martensite. Step 4: Elimination of Incorrect Options
- Bainite, Pearlite, and Ledeburite all form through diffusional transformations, not via the coordinated distortion model. Conclusion: The Bain distortion model explains the atomic mechanism of martensitic transformation.