Texture and quantitative phase analysis of aged Ni-rich NiTi using X-ray and neutron diffractions

The present paper reports X-ray diffraction (XRD) and neutron diffraction (ND) results which were obtained for a Ni-rich NiTi shape memory alloy (SMA). The phases 132, R, B19' and Ni4Ti3 were considered. It has been shown that XRD results for NiTi alloys strongly depend on the type of surface preparation. Moreover it is shown that XRD and ND results can differ considerably. We conclude that the micro structures in the surface region (analyzed by XRD) and in the bulk (analyzed by ND) differ in terms of detected phases and corresponding volume fractions. The diffraction data were analyzed using the Rietveld refinement with the GSAS software package. Good agreement between measured and calculated data was obtained in all cases when the generalized spherical harmonic (GSH) description for preferred orientation (PO) correction was included in the refinements. The quality of the RR fits was better for the ND than for the XRD patterns.