Canadian Welding Bureau (CWB) Level 3 Practice Exam

The grain growth tends to do what with the surface energy?

Increase Equal No change Lower

Correct Answer:

Lower

Explanation:

Grain boundaries carry higher energy than the crystal interior, so the system tends to minimize this interfacial energy. When grains grow, many small grains disappear and merge into larger ones, which reduces the total grain boundary area. Since the grain boundary energy contributes to the overall surface energy of the material, lowering the boundary area decreases the surface energy of the system. In short, grain growth acts as a thermodynamic drive to reduce surface energy by reducing the total grain boundary area.

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