A normal cast or forged piece of metal is composed of numerous (nearly) microscopic crystals of the metal alloy. They're often called "grains", and the boundaries between the grains can tend to weaken the structure or be focal points for defects.
It is possible (and the technology isn't new) to form metal parts in complex shapes which are composed of a single crystalline structure. They have no grains and no grain boundaries. Consequently, they are structurally much stronger, and can therefore be much lighter, than conventional polycrystalline parts.
A common application of this technology is jet engine turbine blades.
I am not a metallurgist.
I am not a metallurgist either but I’ve some blacksmithing experience, and you have a superb grasp of the concept.
Thank you both for your explanations on single crystal.
I think one of the things NTSB will be investigating is whether sub-quality counterfeit parts made it into the maintenance supply flow.
I stayed at a Holiday Inn Express once.
So here you go.