Formation of bulk (Zr, Ti)-based metallic glasses

In six bulk metallic glass-forming (Zr, Ti)-based Be-free alloys (Zr50Ti16. 5Cu15Ni18.5, Zr40Ti10Cu50, Zr69.5Cu12Al7.5Ni11, Zr65Cu17.5Ni10Al7.5, Zr57Ti 5Cu10Ni8Al10, and Zr52.5Ti5Cu17.9Ni14.6Al10) the structure of the equilibri um crystalline phases and their volume fraction were determined by quantita tive analysis of X-ray diffraction. The equilibrium microstructure of all t hese alloys consists of a mixture of ternary (one or two) and binary (one o r two) phases in a ratio close to 0.4:0.6. By thermal analysis and jet cast ings a temperature range was found in the melt which we call 'undercoolable melt' (UCM): cooling from this range results in an increase of undercoolin g and glass-forming ability (GFA). These results can be explained assuming a concurrence of a syntectic reaction (i.e, solid state compound formation from separated liquids) with a eutectic one prior to solidification. (C) 19 99 Elsevier Science B.V. All rights reserved.