Structure of rapidly quenched (Cu_0.5Zr_0.5) _100-xAg_x alloys (x = 0-40 at.%)

The influence of Ag addition on the microstructure of rapidly quenched (Cu_0.5Zr_0.5)_100-xAg _x melts was investigated (x = 0-40 at.%). Fully glassy alloys were obtained for 0 ≤ x ≤ 20 at.% Ag, which are characterized by a homogeneous microstructure without any indication of phase separation. For 30 ≤ x ≤ 40 at.% Ag a composite structure is formed consisting of fcc-Ag nano-crystallites 5 nm in size and an amorphous matrix phase Cu₄₀Zr₄₀Ag ₂₀. With higher Ag-content the volume fraction of the fcc-Ag phase becomes increased mainly due to crytal growth during quenching. The primary formation of fcc-Ag for 30 ≤ x ≤ 40 at.% Ag is confirmed by the analysis of the microstructure of mold cast bulk samples which were fully crystalline. From the experimental results we conclude that the miscibility gap of the liquid phase of the ternary Ag-Cu-Zr system may occur only for x > 40 at.% Ag. For the bulk glass forming quaternary Cu₄₀Zr₄₀Al ₁₀Ag₁₀ alloy a homogeneous element distribution is observed in accordance with the microstructure of ternary (Cu _0.5Zr_0.5)_100-xAg _x glasses (x = 10, 20 at.%).