Novel Ti-based bulk metallic glasses with superior plastic yielding strength and corrosion resistance

Novel Ti-Zr-Cu-Co-Sn-Si-Ag bulk metallic glasses (BMGs) with the critical diameter up to 5 mm were successfully prepared by using copper mold casting method. It is shown that the BMG with best glass forming ability (GFA) is evolved from β-Ti+α-Ti+Ti2Cu+Glass, and β-Ti+α-Ti+Glass with the substitution of Ag for Cu from zero to 4 at%. The thermal stability investigations show that the enhanced GFA is associated to the decrease of the melting temperature and the increase of activation energy of crystallization by addition of Ag. A record yielding strength up to 2.6 GPa as well as yielding strain up to 2.55% were measured in this kind of BMGs. It is found that the shear fracture mechanism of this kind of BMGs basically agrees with the Tresca criterion. Multiple shear bands and well developed vein patterns were clearly observed, reflecting that plastic deformation takes place. The electrochemical polarization experiments show that this kind of BMGs exhibits higher corrosion potential and lower corrosion current density compared with Ti-6Al-4V alloy in four different kinds of corrosion solutions.