Formation of Nanocrystalline Globules and Metallic Glass in Fe_70−xCu_xZr₁₀B₂₀ (x=0–70) Alloys

Abstract

The microstructure in rapidly-solidified Fe_70−xCu_xZr₁₀B₂₀ (x=0, 10, 20, 30, 35, 60 and 70) alloy ribbons prepared by single-roller melt-spinning method was examined. In spite of the positive heat of mixing in Fe–Cu atom pair, metallic glass was formed in Fe–Cu–Zr–B ribbons. F.c.c.–Cu nano crystalline globules dispersed in Fe–Zr–B based metallic glass was formed in Fe₆₀Cu₁₀Zr₁₀B₂₀ and Fe₅₀Cu₂₀Zr₁₀B₂₀ alloys. Size of the globules in nano-emulsion structure increased with increasing Cu concentration. In Fe₃₅Cu₃₅Zr₁₀B₂₀ and Fe₁₀Cu₆₀Zr₁₀B₂₀ alloys, an entangled marble-like duplex structure composed of Fe-rich and Cu-rich crystalline phases was formed. Zr and B additions in Fe–Cu based alloys cause the formation of metallic glass and unique solidification structures in rapidly solidified melt-spun ribbons.