What is the effect of strain hardening on a ductile metal?

• A. It becomes softer and weaker
• B. It becomes harder and stronger
• C. It becomes more ductile
• D. It remains unchanged

Answer: (B)

Strain hardening increases dislocation density and makes dislocations interfere with each other, so their motion becomes harder. As a result, the stress required to continue deforming rises, and the metal becomes harder and stronger (higher yield and tensile strength). At the same time, this dislocation forest reduces the material’s ability to undergo further plastic deformation, so ductility decreases. So the effect is to harden and strengthen, not soften, remain unchanged, or become more ductile.