Role of small atoms in the formation and properties of Zr-Ti-Cu-Ni-Be bulk amorphous alloys

The formation, thermal stability and mechanical properties of ZrTiCuNiBe bulk amorphous alloy were investigated by means of x-ray diffraction, differential scanning calorimetry and microhardness measurements. The amorphous alloys Zr41Ti36.5-xCu12.5Ni10Bex in the composition range 15 less than or equal to x less than or equal to 32 at. % were prepared to investigate the role of Be in the glass forming ability. It is found that the formation, crystallization, and thermal properties of the amorphous alloy are sensitive to the addition of small sized atoms of Be. The amorphous alloy becomes more stable with increasing Be contents. A small amount of carbon addition can further extend the supercooled liquid range and enhance the strength of the alloy. More carbon additions result in the formation of a crystalline/amorphous mixture accompanied by a pronounced increase in strength. The role of Be and C in the excellent glass former alloys is discussed in terms of the thermodynamic and microstructural aspects. The decomposition phenomenon in the Zr41Ti14Cu12.5Ni10Be22.5 alloy is interpreted based on the experimental results. The effects of carbon on the strength of the alloy are discussed from a structural point of view. (C) 1998 American Institute of Physics. [S0021-8979(98)00823-8]