Structural phase transitions in the Ti₄₅Zr₃₈Ni_17-xFe_x nano-alloys and their deuterides

Abstract The mechanically alloyed Ti-Zr-Ni materials are extensively studied due to their promising properties concerning biomedical, electronic or hydrogen related applications (for example the gaseous hydrogen storage and the MNiH batteries). In this paper we address the very crucial issue of the structural properties and transformations of the amorphous and quasicrystalline Ti₄₅Zr₃₈Ni_17-xFe_x (x = 0, 4, 8) and their hydrides. According to the neutron diffraction results, the transformation of the amorphous Ti₄₅Zr₃₈Ni₁₇ phase into the icosahedral quasicrystalline state (the i-phase) is quasi-continuous and starts at the relatively low temperature of 300°C. At 500°C the i-phase is well-developed. At higher temperatures the i-phase transforms into the approximant w-phase and eventually into the cubic phase (the c-phase). Interestingly, the deuterided i-phase exhibits completely different thermal evolution. Namely, this phase decomposes into the simple intermetallic compounds above 625°C. What is worth-mentioning is that the release of deuterium is strictly related to that structural decomposition. The possibility of hydrogenation of the amorphous Ti₄₅Zr₃₈Ni_17-xFe_x phases with maintaining the amorphous nature of the alloys is the other extremely important field of our interest. We established a processing route to meet our goal. Finally, we show that introducing deuterium triggers an exciting phase transition from the deuterided amorphous phase into the unknown before, partially disordered, quasicrystalline-like phase (the glassy quasicrystal) without releasing of deuterium.