Intermetallic phase formation during annealing of Al/Ni multilayers

Abstract

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.

Direct characterization of phase transformations and morphologies in moving reaction zones in Al/Ni nanolaminates using dynamic transmission electron microscopy

“…Diffraction As the hot reaction front passes the observation area probed by the electron pulse, background intensity increases and the diffraction ring patterns become diffuse due to increased thermal diffuse scattering. Seconds later, after the specimen is fully reacted, the samples have converted completely to NiAl without signs of transitions to other phases such as Al 3 Ni 2 or AlNi 3 , unlike other findings from differential scanning calorimetry and x--ray diffraction work of various material systems of nanolaminates [6,23,24]. The result that all three types of these far--from--equilibrium nanolaminates make a single transition to the NiAl phase should be noted since the material systems should form various other intermetallic phases [25] for the 3:2 and 2:3 Al:Ni compositions, when in equilibrium.…”

Interdiffusion of Ni-Al multilayers: A continuum and molecular dynamics study

“…When a small but concentrated pulse of energy such as an electric spark or a thermal pulse is provided, highly exothermic, self-propagating chemical reactions can be triggered that proceed very quickly. The Ni-Al multilayer is often used as model system and as such it has been widely investigated systems both in experiment [1][2][3][4][5] and in continuum studies [6][7][8][9][10][11][12][13][14][15][16]. Recently, these multilayers have received increased attention because of their potential application as controllable, localized heat sources for joining microelectronic components without damage and as useful tools for forming near-net shape intermetallics [17][18][19].…”

X-ray reflectivity measurement of interdiffusion in metallic multilayers during rapid heating

“…If we assume that interdiffusion is dominated by diffusion of nickel [because nickel is known to be a fast diffuser in aluminium (Edelstein et al, 1994)], as a rough approximation we may also take this value of activation energy as representative of interdiffusion. For Ni-rich alloys, Watanabe and co-workers reported higher activation energies for interdiffusion, E a = 214-277 kJ mol À1 (Watanabe et al, 1994).…”