Diffusion mechanism of Zr-based metallic glass during oxidation under dry air

Effect of surface morphology on the oxidation behavior of bulk metallic glass

“…Meanwhile, other researchers claimed that the acceleration effect was caused by the dislocation densification (or grain refining) resulting from surface treatment. The oxidation of metallic materials has been validated to be controlled by the mutual diffusion of anions and cations through the pre-existing oxide scales, and the microstructures of scales and substrates have significant influence on the diffusion process [28].Since BMGs have distinct microstructures in comparison with those of crystalline metals and alloys mentioned above, their oxidation behaviorsare also different, as demonstrated in previous studies [29,30]. Meanwhile, few studies have paid attentions to the influence of surface morphology on the oxidation behavior of BMGs.…”

“…6, the particles preferentially segregate at the top of scratches, while the scale right below the scratch top is thicker than that below the scratch bottom. Since the oxidation process of BMGs is a diffusion-controlled process [30], it is indicated that both the inward diffusion of O and the outward diffusion of Cu go faster at the scratch top area. …”

Air oxidation of a Zr55Cu30Al10Ni5 bulk metallic glass at its super cooled liquid state

“…For Ni cations, since they are not oxidizable and have limited content, they change little during the whole oxidation process except for a Ni-depleted zone in the outer layer of scale. This Ni-depleted zone reveals that the Ni cations are also expelled inward due to the densification of scales and substrates caused by crystallization [11]. …”

“…Cao et al studied the Zr 56 Co 28 Al 16 BMG over the temperature range of 673-923 K, and observed the surface segregation of cobalt [10]. Wang et al investigated the oxidation behavior of Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass and its crystalline counterpart, and found that the oxides grow under concurrent inward O and outward Zr diffusion in short-term oxidation, while for long-term oxidation process the dominant factor turns to be the outward Cu and inward O diffusion [11]. Liu et al studied the air oxidation behavior of Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass both in glassy state and the super cooled liquid state, they argued that the oxidation process is governed by the inward diffusion of O and outward diffusion of Cu, and the inward diffusion of O is dominant [12].…”

Bulk metallic glassy surface native oxide: Its atomic structure, growth rate and electrical properties

“…Thermal oxidation of ZrACu-based BMGs was found to follow one of two mechanisms [31]: either nodules of tetragonal ZrO 2 with embedded nanocrystals of other late transition metals (CuO and ZrO 2 oxides on the surface of Zr 55 Cu 30 Al 10 Ni 5 BMG [32] or Cu 2 O, CuO and tetragonal ZrO 2 on CuAZrAAl BMG [33]); or formation of a lamellar structure of the tetragonal and monoclinic forms of ZrO 2 (Cu 50 Zr 50 and Cu 46 Zr 46 Al 8 metallic glasses [34]). On the other hand layers of CuO/Cu 2 O and a minor fraction of cubic-ZrO 2 were formed on Cu-rich Cu 60 Zr 30 Ti 10 metallic glassy surface [35].…”