Identification of a kinetic length scale which dictates alloy phase composition in Ni-Al interfaces on annealing at low temperatures

Journal Article · Sun Dec 14 00:00:00 EST 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4902965· OSTI ID:22402753

Swain, Mitali; Singh, Surendra; Basu, Saibal; Bhattacharya, Debarati ^[1]; Gupta, Mukul ^[2]

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1. Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)
2. UGC DAE Consortium for Scientific Research, Khandwa Road, Indore 452001 (India)

Ni-aluminides are an important class of intermetallics from technological point of view. Ni-Al phase diagram has been studied in detail experimentally as well as theoretically. It is known that if annealed at low temperature, the first alloy phase is usually NiAl{sub 3} according to Bené's rule. It is also understood that heat of formation may get modified by local densities of the constituents forming the alloy. In this regard, it is important to identify a kinetic length scale for defining “local density” in a system. We have deposited ultrathin multilayers of Ni and Al of layer thickness in tens of nanometres with Ni:Al stoichiometric ratio as 3:1 and 1:3, respectively. Considering these stoichiometry, Ni{sub 3}Al and NiAl{sub 3} are the thermodynamically favoured alloy phases in these samples. We used x-ray reflectivity, polarized neutron reflectivity, x-ray diffraction, and secondary ion mass spectroscopy to follow the alloy formation after annealing and identified the alloy phases at interfaces with nanometre resolution. Diffusion length of Ni and Al was obtained using Darken's law. Our results predict that ‘diffusion length’ is the unique length scale that connects kinetics to local density. In another interesting observation, using “virtual Kirkendall markers” at the interfaces, we showed asymmetry in consumption of Al for alloy formation, at Al on Ni (Al/Ni) and Ni on Al (Ni/Al) interfaces by comparing as-deposited and annealed states with respect to the markers.

• OSTI ID: 22402753
• Journal Information: Journal of Applied Physics, Vol. 116, Issue 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANNEALING
DENSITY
DIFFUSION LENGTH
FORMATION HEAT
INTERFACES
INTERMETALLIC COMPOUNDS
ION MICROPROBE ANALYSIS
NEUTRONS
PHASE DIAGRAMS
REFLECTIVITY
TEMPERATURE RANGE 0065-0273 K
X RADIATION
X-RAY DIFFRACTION