The influence of thermally-induced structural relaxation and crystallization on the mechanical and electrochemical corrosion behaviour of a Zr 60Cu 20Al 10Fe 5Ti 5 metallic glass has been studied. The hardness, H, and reduced Young's modulus, E r, increase upon annealing at 648 K (i.e., close to the glass transition) from H = 6.7 GPa and E r = 79.4 GPa (as-cast state) to H = 7.0 and E r = 86.7 GPa (structurally relaxed state). The influence of the free volume annihilation, caused by the annealing treatments, on these mechanical properties is discussed. Further increase in H and E r occurs after annealing at 873 K, when the sample becomes fully crystalline, probably due to the formation of Zr 2Cu phase. The crystallization also increases the H/E r ratio (which is indicative of the wear resistance), from 0.083 in the as-cast condition to 0.102, whereas structural relaxation does not have a clear effect on this parameter. Annealing close to the glass transition is also beneficial to improve the corrosion resistance and, in particular, the resistance to pitting, when this alloy is immersed in simulated body fluid (Hank's solution). The corrosion potential shifts from -0.214 V to -0.043 V (vs. AgAgCl) and the current density decreases from 3.017 × 10 -4 A/cm 2 to 8.846 × 10 -6 A/cm 2 after annealing at 648 K, mainly because of the free volume reduction. The corrosion potential is maximum (i.e., -0.022 V) and the corrosion density minimum (i.e., 1.428 × 10 -6 A/cm 2) when the sample becomes fully crystalline. © 2012 Elsevier Ltd. All rights reserved.
- B. Glasses, metallic
- B. Mechanical properties at ambient temperature
- F. Corrosion behaviour