Structures, properties and responses to heat treatment of melt-spun Cu - Y alloys

Copper alloys containing up to 7 wt.% Y were prepared by chill-block melt-spinning into ribbons of thickness between 40 to 70 μm. The melt-spun ribbons were heat treated for 2 h at 200, 300, 400, 500, 600 and 800 °C respectively. The as-spun and heat treated ribbons were tested for microhardness and resistivity. The microstructures of these ribbons were investigated by optical and transmission electron microscopy and X-ray diffraction. Microstructures were of the typical Zone A/Zone B type for Cu - 3Y, Cu - 4Y and Cu - 7Y ribbons as-spun and of columnar cell type for Cu - 1Y ribbons as-spun. X-ray diffraction and TEM confirm that on the chill side of the ribbon there were nano-sized αCu with only a small amount of secondary phases. These nano-sized αCu were retained partially after heat treatment up to 600 °C for 2h for Cu - 3Y, Cu - 4Y and Cu - 7Y alloys. The secondary phases were identified by TEM and XRD as Cu₄Y/Cu₅Y. Both αCu and Cu₄Y/Cu₅Y coarsened as a result of heat treatment at 800 °C for 2 h for all the alloys.