Spontaneous softening via recovery

Recovery is basically the recovery pause of the structure after forming or welding. Internal stresses are relieved as dislocations rearrange and cluster into subgrains. The material becomes softer and more relaxed, but loses hardness and strength. When welding, you have to watch out that the heat-affected zone doesn't soften too much. Especially with cold-worked or heat-treated materials, this can cause the weld to no longer meet the required strength. Controlling cooling rate and heat management is key here to maintain the desired properties.