Chemical Engineering Basics - Engineering

Q1:

Fine grained steels have

A high brittleness

B higher tendency to distort

C high ductility

D none of these

ANS:C - high ductility

Fine-grained steels typically have high ductility. The grain size in metals, including steels, plays a significant role in determining their mechanical properties. Finer grain sizes generally result in improved mechanical properties, including higher strength, toughness, and ductility, compared to coarser-grained counterparts. Fine-grained steels exhibit enhanced ductility due to several factors:

  1. Grain Boundary Strengthening: In fine-grained steels, the high density of grain boundaries acts as barriers to dislocation movement, leading to increased strength and ductility.
  2. Uniform Deformation: Fine grains promote more uniform deformation during plastic deformation processes, such as stretching or bending, which enhances the overall ductility of the material.
  3. Resistance to Cleavage Fracture: Fine-grained microstructures are less prone to cleavage fracture, which is a brittle fracture mechanism. Instead, they tend to deform plastically before fracturing, contributing to their higher ductility.
Therefore, fine-grained steels typically exhibit high ductility, contrary to high brittleness or higher tendency to distort.