Nanoscale structure formation in nickel-aluminum alloys synthesized far from equilibrium

Zhehao Chen; Aslak J J Fellman; Katarzyna Mulewska; Kenichiro Mizohata; Davide Gambino; Yanling Ge; Eryang Lu; Flyura Djurabekova; Andreas Delimitis; Lukasz Kurpaska; Kostas Sarakinos; Filip Tuomisto

arXiv · 2501.08530

Nanoscale structure formation in nickel-aluminum alloys synthesized far from equilibrium

Zhehao Chen·Aslak J J Fellman·Katarzyna Mulewska·Kenichiro Mizohata·Davide Gambino·Yanling Ge·Eryang Lu·Flyura Djurabekova·Andreas Delimitis·Lukasz Kurpaska·Kostas Sarakinos·Filip Tuomisto

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Abstract

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). Whereas in the range x=0.11-0.24 the phase coexists with the ordered L12 structure (γ' phase). The two phases are homogenously intermixed forming a coherent and strained nano-solution, 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 nano-solution 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 nano-solution 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.

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Zhehao Chen, Aslak J J Fellman, Katarzyna Mulewska, Kenichiro Mizohata, Davide Gambino, Yanling Ge, Eryang Lu, Flyura Djurabekova, Andreas Delimitis, Lukasz Kurpaska, Kostas Sarakinos, Filip Tuomisto. 2025-06-05. Nanoscale structure formation in nickel-aluminum alloys synthesized far from equilibrium. https://arxiv.org/abs/2501.08530

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