A Cracked Piece of Metal Healed Itself in Experiment That Stunned Scientists

<img width="1024" height="415" src="https://www.sciencealert.com/images/2023/07/BrokenMetal.jpg" alt="Broken metal"/>But how?

https://www.sciencealert.com/a-cracked-piece-of-metal-healed-itself-in-experiment-that-stunned-scientists