Ion beam mixing and phase formation in Ni-Al multilayers studied by RBS and PAC

Ni-Al bi- and multilayers were irradiated with 300-900 keV Xe ions and analysed by Rutherford backscattering spectrometry (RBS) and the perturbed gamma-ray angular correlation (PAC) method. As PAC measures the interaction of radioactive probe nuclei (111In) with hyperfine fields, it is sensitive to changes in the nearest-neighbour surrounding induced by a phase transformation. The formation of the crystalline NiAl phase during irradiation was indeed detected by PAC; it was found to start at ion fluences below that required for complete mixing of the constituents. Similar results were obtained after 600 keV Ar irradiations. The interface mixing rate in Ni-Al bilayers due to 300-600 keV Xe ions was measured with RBS to be k = 4.5(3) x 104 A4 at room temperature. (author)