Question

In cored structure:

• A. There are no composition fluctuations from core to the tip
• B. There are composition fluctuations from core to the tip
• C. Equiaxed structure
• D. Dendritic segregation

Hint:

Cored structures show composition gradients because solute atoms don't have enough time to redistribute during rapid cooling.

Answer 1

The Correct Option is B

A cored structure, also known as microsegregation, forms during non-equilibrium solidification in alloys.
As solidification progresses:
- The early solidified core of the grain becomes enriched with the higher melting point component.
- The remaining liquid becomes richer in the lower melting component and is pushed to the outer regions (towards the grain boundaries or "tip").
This leads to a composition gradient — or fluctuation — from the center of the dendrite (core) to its edge.
This occurs due to insufficient diffusion during fast solidification. It is a common problem in cast alloys and often corrected by heat treatment (homogenization).
Hence, in a cored structure, composition does vary from core to the tip.