Strain rate induced amorphization in metallic nanowires

Using molecular dynamics simulations with a many-body force field, we studi ed the deformation of single crystal Ni and NiCu random alloy nanowires sub jected to uniform strain rates but kept at 300 K. For all strain rates, the Ni nanowire is elastic up to 7.5% strain with a yield stress of 5.5 GPa, f ar above that of hulk Ni. At high strain rates, we find that for both syste ms the crystalline phase transforms continuously to an amorphous phase, exh ibiting a dramatic change in atomic short-range order and a near vanishing of the tetragonal sheer elastic constant perpendicular tb the tensile direc tion. This amorphization which occurs directly from the homogeneous, elasti cally deformed system with no chemical or structural inhomogeneities exhibi ts a new mode of amorphization. [S0031-9007(99)08867-5].