Surface amorphization of NiTi has been achieved by ultra-high strain rate dynamic loading induced by ultrasonic nano-crystal surface modification (UNSM). The amorphous microstructure was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). To better understand the physical mechanism of the amorphization process, molecular dynamics (MD) simulation has been implemented to simulate the shock loading process and the results are consistent with the experiment. Central-symmetry parameter (CSP) and radial distribution function (RDF) were used to characterize the microstructure evolution. The simulation result demonstrates that the deformation is first formed as "twining" structure and then transformed into amorphization. The simulation also shows that shock speeds affect the amorphization level on the surface, while the shock amplitude mainly affects the amorphization depth.
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