Peening is called what process at the same time, which improves fusion structures and avoids possible cracking?

Peening is a process that involves bombarding a material's surface with small spherical media to introduce compressive residual stresses. This helps improve the material's fatigue resistance and overall durability. The correct answer relates closely to annealing, which is a heat treatment process used to alter the physical and sometimes chemical properties of a material.

While both processes aim to enhance structural integrity and reduce the risk of cracking, annealing specifically involves heating a material to a certain temperature and then allowing it to cool slowly. This treatment alleviates internal stresses, refines the grain structure, and enhances ductility, all of which contribute to improved performance and resistance to cracking.

In contrast, tempering and martempering are heat treatment processes associated with hardening and adjusting the toughness of steel, while normalizing adjusts the grain structure to improve mechanical properties but doesn't apply the same principles of surface enhancement as peening does. Thus, annealing is the most relevant process here, as it is known for enhancing fusion structures and mitigating potential cracking, aligning seamlessly with the concept of peening.