Question

Why poly crystals are stronger than single crystals?

Answer 1

Orientation of small grains in polycrystalline materials are inconsistent in nature. Large number of grain boundaries and interfaces contribute to their outstanding strengthening ability. Also, orientation of some grains along applied stress direction enhances the strength.

Dislocations are unable to cross grain boundaries, making them more strong. Deformation is not possible in polycrystalline materials like single crystals as it is not easy to deform the small small single crystals of which it is composed of, thanks to the surroundings and grain boundaries.