Several melt-spun ribbons of different compositions in the Al-rich corner of the Al-Ni-Sm ternary system were analysed by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) in order to determine their thermal stability and to understand the nanocrystallisation process. Out of all the compositions analysed, only three were found to be completely amorphous, whereas the others were partially crystallised. The activation energies of the α-Al nanocrystallisation were evaluated using the Kissinger method. Isothermal DSC scans revealed the existence of quenched-in nuclei in the more unstable amorphous alloys. These quenched-in nuclei are probably due to the melt-spinning process and the crystalline structure after devitrification is strongly dependent on them. © 2001 Elsevier Science B.V. All rights reserved.