Dynamic damage response of sing-crystal NiTi alloys induced by shear localization

Abstract

This work investigates the dynamic response of a monocrystalline nickel-titanium (NiTi) alloy at the atomic scale. The results deduced from non-equilibrium molecular dynamics modeling demonstrate that no shear deformation band (SDB) appears in the sample at an impact velocity of less than 0.75 km/s. As this velocity increases, shear deformations become pronouncedly localized, and the average spacing between SDBs decreases until it stabilizes. Combining shear stress and particle velocity profiles, the survival of SDBs is found to be closely associated with plastic deformation. The dislocations clustering around SDBs predominantly exhibit 〈100〉 partial dislocations, whereas 1/2〈111〉 full dislocations are dominant in those regions without SDBs. Void nucleation always occurs on SDBs. Subsequently, void growth promotes a change in the SDB distribution characteristic. For the case without SDB, voids are randomly nucleated, and the void growth exhibits a non-uniform manner. Thus, there is an interaction between shear localization and void evolution in the NiTi alloy subjected to intensive loading. This study is expected to provide in-depth insights into the microscopic mechanism of NiTi dynamic damage.