Ti-based bulk glassy composites obtained by replacement of Ni with Ga

This article evaluates the possibility to replace nickel by gallium, which is considered non-toxic for biomedical use, in a Ti-based bulk metallic glass. A new alloy with the atomic composition Ti41.5Zr2.5Hf5Cu37.5Ga7.5Si1Sn5 free of Ni and other toxic elements was designed and manufactured by means of suction casting the molten alloy into copper molds. Cylindrical rods with diameters up to 3 mm and a length of 50 mm were successfully produced. Further investigations by differential scanning calorimetry and X-ray diffraction in Bragg-Brentano configuration, as well as in transmission using synchrotron radiation, evidenced the main crystalline phases in the new alloy, together with a small content of amorphous matrix. Further in-depth analyses using scanning electron microscopy coupled with elemental mapping, high-resolution transmission electron microscopy and high-angle annular dark-field imaging, revealed a fine microcrystalline structure consisting of γ-CuTi and complex GaTi/CuGaTi intermetallics, together with a remnant amorphous matrix. Such kind of composite samples may open the door for new biomedical devices.