High Strain Rate Compression of Martensitic NiTi Shape Memory Alloys

Abstract

The compressive response of martensitic NiTi shape memory alloys (SMAs) under high strain rate (1200 s−1) was investigated on a modified Kolsky (Split Hopkinson) compression bar. The single-loading momentum trapping system ensures precise deformation control (1.4, 1.8, 3.0, 4.8, and 9.6 % strain) and single loading during dynamic compression. With increasing strain, the phase transformation peaks shift toward lower temperatures, while the intensities of these peaks decrease and eventually disappear completely at strains above ~7 %, where the onset of plastic deformation of reoriented martensite occurs. All transformation peaks are recoverable after deformation simply by annealing at 873 K (600 °C) for 30 min, except those peaks corresponding to strains above ~7 % (e.g., 9.6 %) which return upon annealing, but at a lower temperature. XRD results showed the variation of the strongest diffraction peak from (1 $$\bar{1}$$ 1) to (111) crystal plane before and after high strain rate compression.