Phase transition in Ti50Ni44Fe6 studied by x-ray fluorescence holography

The phase transition behavior of the local structure around Fe in a shape-memory-alloy-related material, Ti50Ni44Fe6, was evaluated by x-ray fluorescence holography. The Fe K alpha holograms were recorded at 225 and 100 K, which correspond to the parent and commensurate phases, respectively. The atomic images at both the phases show that the first neighbor Ti atoms around Fe, fluctuating in the parent phase, is strongly stabilized in the commensurate phase and that a clusterlike structure with a radius of 8 A degrees is formed in this lower temperature phase. These dynamically structural changes offer important keys to understanding the precursors to the martensite phase transition of the TiNi series.