Crystallisation of amorphous Al-Y-Ni-(Cu) alloys

The nanocrystallisation behaviour and subsequent intermetallics formation of an amorphous Al-88-Y-4-Ni-8 alloy has been studied. A 1 at.% of Al or Ni was also substituted by Cu and its effect studied. Differential scanning calorimetry has been used to measure the thermal stability of these amorphous alloys. Transmission electron microscopy showed the smaller size of the nanocrystals obtained during primary crystallisation when Cu is added. Using three-dimensional atom probe, it has been checked that Cu is homogeneously distributed in the amorphous matrix, not contributing to a heterogeneous nucleation around Cu clusters during the formation of nanocrystals. Transmission electron microscopy and X-rays diffraction are used to study the controversial intermetallics occurrence at higher temperatures. The sequence and characteristics of the intermetallics appearing in these alloys were sensitive to the presence of Cu. The evolution of these intermetallics, up to 600 degrees C, has been studied. Findings are compared with previous studies.