Solidification processes in Cu–Zr–Ag amorphisable alloy system

Abstract

Abstract The Cu–Zr–Ag system is one of Cu−Zr based bulk metallic glasses (BMG) that has been in the center of great interest for a long time. This work summarizes results on solidification in the Cu–Zr–Ag ternary alloys and relationship between the cooling rate and their microstructure. The alloys in a wide range of compositions were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) techniques. The surface of stable liquidus miscibility gap has been presented by isothermal sections in this system. The central part of liquidus projection of the ternary Cu–Zr–Ag system is determined based on the harmonization of experimental results and the calculated phase diagrams. Due to the liquid separation, amorphous/crystalline composites could be obtained with a silver content up to 50 at%. The primary solidified phases were identified in different samples cooled with a controlled cooling rate (5 K/min), in the arc melting furnace (master alloys) and in a wedge shape mould. It has been shown that the m-phase (or AgCu 4 Zr) has the lowest and the (CuAg) 10 Zr 7 the highest driving force for nucleation in this system. It has been shown that the glass forming ability depends not only on the properties of atomic constituent but on the phases formed during the solidification of undercooled liquid.