Volume 7, Issue 2 (February 2010)
Glass Formation and Mechanical Properties of Ti–Cu–Ni Alloys with High Ti Content
A series of Ti–Cu–Ni alloys with Ti content as high as 50–70 at. % expected to possess potential high glass-forming ability (GFA) was designed according to the ε criterion (Xia, M. X., Zhang, S. G., Ma, C. L., and Li, J. G., “Evaluation of Glass-Forming Ability for Metallic Glasses Based on Order-Disorder Competition,” Appl. Phys. Lett. Vol. 89, 2006, pp. 091917-1–091917-3) and were prepared by melt spinning and suck casting methods. The samples were examined by X-ray diffractometry, differential scanning calorimetry, optical microscopy, scanning electronic microscopy, and quasistatic compression test. The GFA of the melt-spun ribbons is enhanced with increasing ε. Ti58Cu32Ni10 alloy with the maximum designed ε value of 0.542 exhibits best GFA with a glass transition temperature of 627 K and a wide supercooled liquid region of 45 K. However, this alloy failed to form a fully glassy rod of 1 mm in diameter. Room temperature compression tests reveal that the 1 mm diameter Ti58Cu32Ni10 glass composite exhibits work-hardening characteristic, with ultimate compressive stress of 2418 MPa, yielding stress σ0.2 of 1448 MPa and about 7.8 % plastic strain. The combination of high strength and ductility was attributed to a dendritic TiCu(Ni) network embedded in the hard glass matrix.