Influence of the irradiation temperature on the surface structure and physical/chemical properties of Ar ion-irradiated bulk metallic glasses

Surface treatments using multiple Ar ion irradiation processes with a maximum energy and fluence of 200 keV and 1 × 1016 ions/cm2, respectively, have been performed on two different metallic glasses: Zr55Cu28Al10Ni7 and Ti40Zr10Cu38Pd12. Analogous irradiation procedures have been carried out at room temperature (RT) and at T = 620 K (≈0.9 Tg, where Tg denotes the glass transition). The structure, mechanical behavior, wettability and corrosion resistance of the irradiated alloys have been compared with the properties of the as-cast and annealed (T = 620 K) non-irradiated specimens. While ion irradiation at RT does not significantly alter the amorphous structure of the alloys, ion irradiation close to Tg promotes decomposition/nanocrystallization. Consequently, the hardness (H) and reduced Young's modulus (Er) decrease after irradiation at RT but they both increase after irradiation at 620 K. While annealing close to Tg increases the hydrophobicity of the samples, irradiation induces virtually no changes in the contact angle when comparing with the as-cast state. Concerning the corrosion resistance, although not much effect is found after irradiation at RT, an improvement is observed after irradiation at 620 K, particularly for the Ti-based alloy. These results are of practical interest in order to engineer appropriate surface treatments based on ion irradiation, aimed at specific functional applications of bulk metallic glasses.