How Hydrogen Decrepitation Works
Hydrogen is a very small and very reactive atom (the smallest atom- comprised of just one proton and one electron) that easily penetrates the grain boundaries of many metals. In most situations, metallurgists try to prevent hydrogen from entering the metal.
Hydrogen embrittles metals by entering the grain boundaries and creating pressure at the weakest point. This causes micro-cracks that begin to propagate through the grain structure.
The Procedure -Using Hydrogen Decrepitation in Neodymium Magnets
While the grains are very small from strip casting with rapid solidification, the material from strip casting comes out of the caster in flakes that must be reduced to powder in order to make magnets. These metal flakes are placed in a vessel under vacuum and a small amount of hydrogen is introduced into the vessel.
As the hydrogen collects in the grain boundaries, the metal begins to disintegrate as can be seen in the short video above.
The decrepitated material is now ready for the next step in the process, where it will be jet-milled to achieve the correct grain size and shape.