Question

Martensitic transformations

• A. Are diffusion controlled
• B. Yield two products of different composition
• C. Are shear processes
• D. Yield a soft product in steels

Hint:

Martensitic transformations result in hard, brittle steel that requires tempering (controlled reheating) to improve toughness.

Answer 1

The Correct Option is C

Martensitic transformation is a phase transformation that occurs in steel when it is cooled rapidly from the austenite phase (quenching), resulting in a hard, brittle microstructure. Step 1: Understanding Martensitic Transformation - Unlike diffusion-dependent phase transformations, martensitic transformations do not involve atomic diffusion. - The transformation is shear-dominated and occurs when the atoms in the crystal lattice shift without diffusion, leading to a change in crystal structure.


Step 2: Evaluating the Options - Option (A) - Incorrect: Martensitic transformations are not diffusion-controlled; they occur instantly without the movement of atoms over long distances. - Option (B) - Incorrect: Martensite has the same composition as the parent austenite phase, so it does not yield two products of different compositions. - Option (C) - Correct: Martensitic transformations are shear-dominated processes, meaning that atoms in the lattice shift to create a new structure. - Option (D) - Incorrect: Martensite is a hard and brittle phase, not a soft product in steels.


Step 3: Conclusion Martensitic transformations are shear processes that occur rapidly and result in a hard, brittle material, making option (C) the correct answer.