Formation ranges of icosahedral, amorphous and crystalline phases in rapidly solidified Ti-Zr-Hf-Ni alloys

Abstract

From the quaternary Ti-Zr-Hf-Ni phase diagram, the cross-section at 20 at.% Ni was selected for investigation. The icosahedral quasicrystalline, crystalline and amorphous phases were observed to form in nine kinds of rapidly solidified (Ti_xZr_yHf_z)₈₀Ni₂₀ (x + y + z = 1) alloys at different compositions. The quasilattice constants of 0.519 and 0.531 nm were obtained for the icosahedral phase formed in the melt-spun Ti₄₀Zr₂₀Hf₂₀Ni₂₀ and Ti₂₀Zr₄₀Hf₂₀Ni₂₀ alloys, respectively. The icosahedral phase formed in the melt-spun Ti₄₀Zr₂₀Hf₂₀Ni₂₀ alloy especially is thermodynamically stable. The supercooled liquid region of the Ti₂₀Zr₂₀Hf₄₀Ni₂₀ glassy alloy reached 64 K. From these results a comparison of quasicrystal-forming and glass-forming abilities was carried out. The quasicrystal-forming ability was reduced and glass-forming ability was improved with an increase in Hf and Zr contents in the (Ti_xZr_yHf_z)₈₀Ni₂₀ alloys. On the other hand, an increase in Ti content caused an improvement in quasicrystal-forming ability.