A comparative study of primary Al precipitation in amorphous Al87Ni7La5Zr by means of WAXS, SAXS, TEM and DSC techniques

The crystallisation behaviour of melt spun amorphous ribbon of Al87Ni7La5Zr alloy was studied. The transformed fraction of the a-Al phase which forms in a primary reaction from the amorphous matrix was determined by means of WAXS, SAXS and DSC measurements. There is a marked difference in the results given by different techniques. Transformed fractions obtained with XRD refer to the real crystal weight (volume) fraction which is lower than that obtained from DSC. The difference may be accounted for by the heat released due to matrix homogenisation, which is diffusion controlled and overlaps with this stage of crystallisation. Crystal shape, size and distribution were analysed by TEM and SAXS obtaining a clear picture of the microstructure made of fine a-Al crystals grouped in clusters.