Intermetallic phase formation during arnnealing of AI/Ni muMayers

The phase evolution during annealing of AlJNi multilayer samples prepared by ion-beam sputtering with composition modulation wavelengths A between 10 and 400 nm was determined using x-ray diffraction and differential scanning calorimeter measurements. Samples with average compositions of &n,N10,6,, and Al,,,N&,~ were investigated. For the Al,,40Ni0.60 samples the following results were obtained. A measure of the degree of periodic@ and the sharpness of the interfaces in a sample with A=80 mn was the large number (over 20) of peaks observed in small-angle x-ray scattering measurements. A sample with A=10 nm was transformed by heat treatment directly to the AlNi phase. In the A=80 nm sample, the first phase formed after annealing was the metastable Y,I phase. The r] phase was identified as Al,Ni,. In the 400 nm wavelength sample, both the metastable 17 phase and the stable Al,Ni formed after the first exothermic reaction. For the Alr,75Ni0,25 samples two results were obtained. A A=11.4 nm sample transformed directly on annealing into Al,Ni. The 77 phase was the first phase formed on annealing a A=100 nm sample. The difference in the component diffusivities and the concentration gradient play an important role in controlling phase formation and evolution.