Effect of cobalt microalloying on the glass forming ability of Ti-Cu-Pd-Zr metallic glass

Microalloying Co to a Ti-Cu-Pd-Zr bulk glass former would affect its glass-forming ability (GFA) and this was investigated by the tilt copper mold-casting technique. The base alloy Ti40Zr10Cu36Pd14 has a critical glass-forming diameter of 5 mm and this was increased significantly to 10 mm for 1 at.% Co replaced with Ti as a Ti39Zr10Cu36Pd14Co1 alloy. The reason for this microalloying induced drastic increase in GFA is discussed with molecular dynamics (MD) simulations. The calculated results reveal that the Co atoms effectively connect isolated atoms and isolated bonds in network formed in the base alloy. Therefore, a larger network is formed and efficiently delays any atomic rearrangement of the crystal structure, and as a matter of fact, enhances the GFA of the Co substituted BMG. This Ni-free Ti-based BMG exhibits good plasticity and a high fracture strength of about 1960 MPa with a low Young's modulus of 93 GPa. Additionally, it has better corrosion resistance compared with the base alloy in a simulated body fluid and is thus expected to find application as a biomaterial.