Institute of Fundamental Technological Research

The results of X-ray diffraction studies on structural changes in the near-surface layers in the NiTi alloy caused by nitrogen-ion implantation with the energy E = 50 keV and the fluence D = 1018cm°2 are presented. X-ray diffractometry, using the Philips diffractometer type X’Pert in the Bragg–Brentano geometry, was used to identify the phase composition of NiTi alloy. For layer by layer analysis of structural changes in the near-surface layers, the D8 Discover Bruker diffractometer with polycapilar beam optics was used. The ion-implanted NiTi alloy in the near-surface layer exhibits five phases: the dominating austenite phase, two martensitic phases and a small amount of the Ni4Ti3 and NTi phases. Along with the decreasing thickness of the near-surface layer investigated in material an increasing fraction of the Ni4Ti3 and NTi phases was observed. With the thickness of this layer about 340 nm, besides still existing the austenite, Ni4Ti3 and NTi phases, only one martensitic phase is present in the alloy. Further decrease of the thickness of the near-surface layer to about 170 nm leads to the increasing fraction of the Ni4Ti3 and NTi phases.

X-ray diffraction, ion implantation, shape memory alloy, nitinol, phase composition