Rapidly solidified Al85Ni15-xYx(x=5,8,10) alloys

The crystallisation behaviour and microstructural development during annealing of amorphous melt-spun Al85Ni15-xYx(x=5,8,10) ribbons have been investigated by a combination of differential scanning calorimetry (DSC), high resolution electron microscopy(HREM), wavelength dispersive microanalysis (WDS) and X-ray diffractrometry(XRD). The initial crystallisation peak of the amorphous Al85Ni15-xYx(x=5,8,10) alloys shows an increasing onset temperature from 210 degrees C to 265 degrees C and an increasing activation energy from 221kJ/mol to 240kJ/mol with increasing Y content from 5 to 10at.%. In addition, the onset crystallization temperature of amorphous Al85Ni5Y10 increases from 225 degrees C to 265 degrees C with increasing circumferential wheel speed from 8m/s to 47m/s. Isothermal annealing for one hour at temperatures in the range 260-400 degrees C produces microstructures consisting of a mixture of alpha-Al, Al3Y, AlYNi and Al3Ni phases. This paper describes in detail the effects of alloy composition and wheel speed on the mechanism and kinetics of crystallisation and subsequent solid phase transformations.