Dynamic mechanical properties and microstructure evolution of NiTi shape memory alloy under high strain rate loading: Plate impact experiments and molecular dynamics simulations

ZH Lin and QK Wang and Y Cai and YT Chen and HY Ma and SP Zhao and NB Zhang and L Lu and SN Luo, JOURNAL OF ALLOYS AND COMPOUNDS, 1046, 184786 (2025).

DOI: 10.1016/j.jallcom.2025.184786

The occurrence of the martensitic phase transformation is still controversial for the austenitic NiTi alloy under shock loading due to the lack of structure information, and its spall damage mechanisms are unclear. Impact responses of shape memory alloy Ni50.6Ti49.4 are investigated via plate impact experiments and molecular dynamics (MD) simulations. In the experiments, free surface velocity profiles are captured via laser Doppler velocimetry. Microstructural characterizations of postmortem samples indicate no austenite to martensite transformation. Plastic deformation is mainly achieved via dislocation slip and kink band. The spall strength is similar to 2.79-3.23 GPa, and weakly dependent on peak shock stress. During spall damage, intragranular cracks are predominant. Both ductile cracks along the 110 primary or 112 secondary slip planes, and brittle cleavage cracks along 001 planes are observed. MD simulations provide atomistic structural evolution during deformation and spall damage. With increasing impact velocity, the dominant (111) pencil dislocations result in a weak texture with the (104) direction parallel to the loading direction. Voids prefer to nucleate at grain boundary triple junctions. In this work, the controversy over whether a phase transformation occurs in the austenitic NiTi SMA under shock loading, and the mechanisms of deformation and spall damage are clarified through detailed microstructural characterizations and MD simulations.

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