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

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