Nanocrystallization behaviour of Al–Y–Ni with Cu additions

This paper reports the results of a short investigation into the effect of Cu additions upon the nanocrystallization behaviour of an Al–Y–Ni alloy. 1 at.% Cu was added to a base alloy of Al88Y4Ni8 either by substitution for Al to form Al87Y4Ni8Cu1, or by substitution for Ni to form Al88Y4Ni7Cu1. Consistent with previous findings in the literature, the substitution of Cu for Al was found to increase the thermal stability of the amorphous phase, whereas the substitution of Cu for Ni was found to decrease its thermal stability. Comparing the microstructures of these alloys after heat treatment to produce equivalent volume fractions of Al nanocrystals showed average grain sizes of ∼14, ∼12 and ∼9 nm for the alloys Al88Y4Ni8, Al87Y4Ni8Cu1 and Al88Y4Ni7Cu1, respectively. The effect of Cu in refining the size of the nanocrystals was attributed to enhanced nucleation increasing the number density of the nanocrystals, rather than diffusion limited or interface limited growth. Further investigation of this behaviour requires direct characterization of the local partitioning behaviour of the Cu during crystallization.