Strain-Induced Ultrahard and Ultrastable Nanolaminated Structure in Nickel

Taking the Strain When heavily deformed through compressive or torsional loading, crystalline metals will generate an increasing density of defects or dislocations that effectively strengthens the metal against further deformation. However, at some stage, the fine-grained structure that forms saturates. Liu et al. (p. 337 ; see the Perspective by Ramtani ), show that combining the application of a very-high-rate shear deformation with high strain gradients to the surface layer of a pure sample of nickel can overcome this saturation. Instead of a three-dimensional fine-grained structure, a top layer with a two-dimensional layered structure occupied the first 80 micrometers. In addition to being stronger, this layered nickel structure was also more thermally stable.