Formation of nanocrystalline particles in glassy matrix in melt-spun Mg--Cu--Y based alloys

Abstract

This paper reports the crystallization sequence of ternary Mg₆₅Cu₂₅Y₁₀, Mg₈₀Cu₁₀Y₁₀ and Mg₈₀Cu₁₅Y₅ amorphous alloys. Nanodispersions of Mg₂Cu, hcp-Mg and fcc-Mg ranging from 5 to 20 nm have been observed in the melt-spun Mg₆₅Cu₂₅Y₁₀, Mg₈₀Cu₁₀Y₁₀ and Mg₈₀Cu₁₅Y₅ alloys, respectively. The brittleness of melt-spun Mg--Cu--Y based alloys appears to be due to the nanodispersions of Mg₂Cu intermetallic phase. On the other hand, nanodispersions of terminal solid solution such as hcp-Mg or fcc-Mg in the amorphous matrix lead to good ductility in the melt-spun Mg-rich alloys. The results also indicate that the glass forming ability and the thermal stability of amorphous phase are not improved by additions of quaternary elements such as Ni, Al, Zn and Mm to Mg--Cu--Y based alloys.