Researchers from Cornell University and the Army Research Laboratory have devised a new method for designing metals and alloys that can withstand extreme impacts. When a metallic material is struck at an extremely high speed, it immediately ruptures and fails. The reason for that failure is embrittlement – the material loses its ability to bend without breaking – when deformed rapidly. The researchers created a nanocrystalline alloy made of copper and tantalum in which dislocations could barely move more than a few nanometers before they were stopped in their tracks, effectively suppressing embrittlement. Dislocations are tiny defects that move through a crystal. During rapid, extreme strains, the dislocations accelerate and interact with lattice vibrations, which create substantial resistance that leads to embrittlement.
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