What results from repeated mechanical work at room temperature?

What results from repeated mechanical work at room temperature?

• A. Gating of grain boundaries
• B. Cold working, strain hardening
• C. Artificial aging
• D. Stress cracking

Answer: (B)

When you deform a metal at room temperature, the material undergoes plastic deformation without heat input. This builds up a high density of dislocations; as these dislocations multiply and interact, they impede each other’s motion. The metal becomes stronger and harder, but less ductile. This combination is described by cold working as the process and strain hardening as the resulting change in properties. That’s why the best choice is cold working, strain hardening. Gating of grain boundaries isn’t a standard outcome of mechanical work at room temperature, artificial aging is a heat-treatment effect, and stress cracking is a failure mode, not the property change from plastic deformation.

When you deform a metal at room temperature, the material undergoes plastic deformation without heat input. This builds up a high density of dislocations; as these dislocations multiply and interact, they impede each other’s motion. The metal becomes stronger and harder, but less ductile. This combination is described by cold working as the process and strain hardening as the resulting change in properties.

That’s why the best choice is cold working, strain hardening. Gating of grain boundaries isn’t a standard outcome of mechanical work at room temperature, artificial aging is a heat-treatment effect, and stress cracking is a failure mode, not the property change from plastic deformation.