Which description correctly characterizes solid-solution strengthening?

• A. Solute atoms distort the lattice and impede dislocations.
• B. Dispersed particles impede dislocations.
• C. Smaller grains hinder dislocation motion.
• D. Dislocations multiply and entangle.

Answer: (A)

Solid-solution strengthening arises when solute atoms in a metal lattice create local lattice distortions that resist dislocation motion. If the solute atoms differ in size from the host atoms, they introduce strain fields around themselves. As dislocations glide through the crystal, these strain regions interact with the dislocations, creating an extra resistance to their movement. This interaction raises the stress required to plastically deform the material, strengthening the alloy without changing the overall phase or adding second-phase particles. The strength increase depends on how many solute atoms are present and how much size mismatch there is, within the solubility limit.

This description matches the concept of solid-solution strengthening because it centers on lattice distortion from solute atoms and the resulting hindrance to dislocation motion. Other descriptions refer to different strengthening mechanisms—dispersion strengthening involves dispersed particles blocking dislocations, grain-boundary strengthening comes from smaller grains hindering movement, and dislocation multiplication/entanglement relates to work hardening and dislocation interactions.