Strain Rate Induced Amorphization in Metallic Nanowires

Hideyuki Ikeda,2 Yue Qi,1 Tahir Çagin,1 Konrad Samwer,2 William L. Johnson,2 and William A. Goddard III1
1Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125
2Keck Laboratory of Engineering Materials, California Institute of Technology, Pasadena, California 91125
Using molecular dynamics simulations with a many-body force field, we studied the deformation of single crystal Ni and NiCu random alloy nanowires subjected 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, far above that of bulk Ni. At high strain rates, we find that for both systems the crystalline phase transforms continuously to an amorphous phase, exhibiting a dramatic change in atomic short-range order and a near vanishing of the tetragonal shear elastic constant perpendicular to the tensile direction. This amorphization which occurs directly from the homogeneous, elastically deformed system with no chemical or structural inhomogeneities exhibits a new mode of amorphization.

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