CAST BULK ZR-TI-AL-CU-NI AMORPHOUS-ALLOYS

Cylindrical bulk amorphous samples with diameters up to 10 mm have bee n prepared by casting Zr-Ti-Al-Cu-Ni alloys in a copper mould. In orde r to rank glass-forming ability as a function of alloy composition, al loys were also cast into wedge-shaped moulds; to a first approximation , the thickness of the amorphous region obtained can be taken as an in dication of glass-forming ability. The compositions which lead to the production of bulk glasses all have reduced glass transition temperatu res in excess of 0.65 and the extremely high glass-forming ability of these compositions is discussed. We suggest that both the Al and Ti co ntents are determining factors for the production of bulk amorphous sa mples and these are believed to reduce the driving force for, and henc e the rate of, crystallisation. These amorphous alloys have been found to display high thermal stability and can be annealed for several min utes in the supercooled liquid region. They are ductile at room temper ature and have a high value of yield stress.