Stress relieving reduces internal residual stresses in a metal by heating to a suitable temperature and holding for a specified time.

• A. Increases internal stresses
• B. Reduces residual stresses by heating and holding
• C. Increases hardness
• D. Removes all grain boundaries

Answer: (B)

Stress relief is a heat-treatment approach that lowers internal residual stresses by heating the metal to a moderate temperature and holding it for a specific time, then cooling slowly. The goal is to let the material’s dislocations and microscopic stress fields rearrange and relax without triggering major changes in the metal’s overall structure. Because the temperature is chosen to avoid recrystallization or significant diffusion, the microstructure and hardness stay essentially the same, though a slight softening from recovery can occur. Grain boundaries remain intact because the treatment is kept below temperatures that would alter the grain structure. In short, this process intentionally reduces internal stresses through controlled heating and holding, which is why the statement describes stress relief accurately.