Hydrogen and Zr-based metallic glasses: Gas/solid absorption process and structure evolution

The absorption of hydrogen by means of gas–solid reaction and its consequence on the structure have been studied for fully amorphous alloys as well as quasicrystals/glassy composite alloys based on the composition Zr59Ti3Cu20Al10Ni8. The process of hydrogen absorption has been performed and monitored under 20 bar of H2 using high pressure-differential scanning calorimetry (HP-DSC). The structure evolution of the samples has been followed by X-ray diffractometry (XRD). Results show that the nature of the surface oxide layer strongly affects the process of hydrogen absorption, especially its starting temperature. The structure evolves nevertheless along the same basic sequence, regardless of the sample: (i) the alloys keep a global amorphous structure up to roughly H/M = 0.8 and T = 350 °C; (ii) then ZrH2 and at higher temperature Cu2AlZr are formed. The stability of the glass is weakened and the formation of quasicrystals is inhibited under 20 bar of H2. An heterogeneous distribution of hydrogen atoms inside the amorphous matrix has been inferred from the results.

Research highlights▶ Surface oxide nature affects strongly hydrogen absorption. ▶ Hydrogen penetration depth is ∼100μm at T<450 °C. ▶ Heterogeneous distribution of hydrogen inside the amorphous matrix. ▶ Alloys can maintain a global amorphous structure up to H/M∼0.8 and T∼350 °C. ▶ H2 atmosphere reduces stability of glass and quasicrystals as well as quasicrystals formation.