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Formation of coherent nanocomposite structure in nickel-aluminum alloys synthesized far from equilibrium

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Title: Formation of coherent nanocomposite structure in nickel-aluminum alloys synthesized far from equilibrium
Authors: Chen, Zhehao, Fellman, Aslak J.J., Mulewska, Katarzyna, Mizohata, Kenichiro, Gambino, Davide, Ge, Yanling, Lu, Eryang, Djurabekova, Flyura, Delimitis, Andreas, Kurpaska, Lukasz, Tuomisto, Filip, Sarakinos, Kostas, 1980
Source: Acta Materialia. 302
Subject Terms: High-resolution tem, Intermetallic, Magnetron sputtering, Metastable alloys, Ni-based alloys, Numerical calculations, Self-organized nanostructures, Thin films
Description: The present study reports on the structure formation in thin epitaxial nickel-aluminum films (Ni1-xAlx; Al atomic fraction x up to x = 0.24 ) grown on MgO ( 001 ) substrates by magnetron sputtering. Experimental and computational data demonstrate that for x < 0.11 , the films exhibit the face-centered cubic random solid-solution Ni1-xAlx structure ( γ phase). Whereas in the range x = 0.11–0.24 the γ phase coexists with the ordered L 1 2 structure ( γ ′ phase). The two phases are homogenously intermixed forming a strained coherent nanocomposite , which exhibits a single lattice parameter that expands as the Al content increases. Isothermal annealing of films containing x = 0.14 of Al, coupled with structural and nano-mechanical characterization, reveal that the coherent nanocomposite retains its overall integrity for temperatures up to 673 K , while the film hardness increases from 5.5 GPa (as deposited films) to 6 GPa . Further increase of the annealing temperature to 873 K and 1073 K causes the coherent nanocomposite to dissolve into distinct γ and γ ′ phase domains and the hardness to decrease down to values of 4 GPa . These findings confirm the metastable nature of the as-deposited thin Ni1-xAlx alloy films and underpin the effectiveness of high supersaturation/undercooling for creating non-equilibrium phases and self-organized nanostructures upon synthesis of multicomponent materials.
File Description: print
Access URL: https://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-373156
https://doi.org/10.1016/j.actamat.2025.121674
Database: SwePub
Description
Abstract:The present study reports on the structure formation in thin epitaxial nickel-aluminum films (Ni<inf>1-x</inf>Al<inf>x</inf>; Al atomic fraction x up to x = 0.24 ) grown on MgO ( 001 ) substrates by magnetron sputtering. Experimental and computational data demonstrate that for x < 0.11 , the films exhibit the face-centered cubic random solid-solution Ni<inf>1-x</inf>Al<inf>x</inf> structure ( γ phase). Whereas in the range x = 0.11–0.24 the γ phase coexists with the ordered L 1 2 structure ( γ ′ phase). The two phases are homogenously intermixed forming a strained coherent nanocomposite , which exhibits a single lattice parameter that expands as the Al content increases. Isothermal annealing of films containing x = 0.14 of Al, coupled with structural and nano-mechanical characterization, reveal that the coherent nanocomposite retains its overall integrity for temperatures up to 673 K , while the film hardness increases from 5.5 GPa (as deposited films) to 6 GPa . Further increase of the annealing temperature to 873 K and 1073 K causes the coherent nanocomposite to dissolve into distinct γ and γ ′ phase domains and the hardness to decrease down to values of 4 GPa . These findings confirm the metastable nature of the as-deposited thin Ni<inf>1-x</inf>Al<inf>x</inf> alloy films and underpin the effectiveness of high supersaturation/undercooling for creating non-equilibrium phases and self-organized nanostructures upon synthesis of multicomponent materials.
ISSN:13596454
18732453
DOI:10.1016/j.actamat.2025.121674