One small correction: "“Annealing” is a process where you heat slowly and cool metal to harden it." Annealing is actually a process to soften metal (and someti

One small correction: "“Annealing” is a process where you heat slowly and cool metal to harden it." Annealing is actually a process to soften metal (and sometimes to remove internal stresses), decreasing strength but increasing ductility and toughness. Like simulated annealing, higher temperature allows the material to jump over larger metastable hills in order to reach a more relaxed, lower energy structure. In annealing, the temperature usually needs to be lowered slowly, because cooling introduces stresses and, to a lesser degree, because the thermodynamically favorable structure changes with temperature. Quenching (cooling quickly) creates residual thermal stresses, and locks in the high temperature structure, which is metastable at lower termperatures.