Transformation of precipitated phases in Zr_50·5Cu_34·5−xNi₄Al₁₁Ag_x alloy master ingots with adding Ag

Abstract

The transformation of precipitated phases of Zr_50·5Cu_34·5−xNi₄Al₁₁Ag_x alloy master ingots with Ag substitution of Cu was studied in detail by phase analysis. The precipitated (Zr–Cu) rich phases deteriorate the glass forming ability (GFA) of Zr_50·5Cu_34·5Ni₄Al₁₁. Two new (Zr–Cu) rich phases, A1 with bcc structure and a = 0·339 nm and A2 with fcc superlattice structure and a = 1·21 nm, were identified by a transmission electron microscope. When x = 2, A1 phase disappears, and A2 phase remains and is suppressed gradually with further Ag addition. When x = 13, one precipitated phase with Ag more than 13 at-% begins to deteriorate GFA. In the view of chemistry, the precipitation of (Zr–Cu) rich phases means that the interaction between Cu and Zr atoms is rather drastic. The addition of Ag weakens the interaction between Cu and Zr. The similar competition mechanism proposed by the authors plays an important role in suppressing precipitated phases and improving GFAs.

Keywords:

• Phase transformation
• Glass forming ability
• Bulk metallic glass
• Microstructure characterisation

The authors gratefully acknowledge the National Natural Science Foundation of China (grant no. 50825402 and no. 50731005).