Effect of Mo Addition on the Formation of Metastable fcc Zr2Ni and Icosahedral Phases in Zr–Al–Ni–Cu Glassy Alloy

Abstract

We investigated the transformation behavior at the initial crystallization stage in the Zr–Al–Ni–Cu–Mo glassy alloy. In the Zr65Al7.5Ni10Cu12.5Mo5 alloy, the crystallization reaction changes to two reactions and the first reaction corresponds to the nanoscale fcc Zr2Ni phase formation. The two-stage crystallization reaction is also observed in the Zr65Al7.5Ni5Cu17.5Mo5 alloy, where the primary phase is the nanoscale icosahedral quasicrystalline phase. The difference in the primary phase between the two alloys is attributed to the difference in the chemical affinities of Mo with Cu and Ni. The formation of nanoscale icosahedral and fcc Zr2Ni phases leads to the hypothesis that the icosahedral short-range order exists in the glassy state of the Zr–Al–Ni–Cu alloy as a unit structure in both phases.