Recrystallization kinetics
The temporal and temperature-dependent regularity of nucleation and grain growth of strain-free crystallites to eliminate internal stresses.
Recrystallization is what happens when you intentionally heat a cold-worked or weld-stressed structure. During this process, new, low-stress crystals form in the grain, making the material softer and more formable again. If you don't manage the heat properly or the cooling is too fast, the structure remains hard and stressed, leading to cracks. Too much heat or too long annealing time also makes the grains too coarse, then the part becomes brittle. For a clean result, you must hit the right annealing temperature and time, otherwise you'll end up with either a hard, crack-prone or a soft, crumbly component.