Abstract
We discuss an atomistic model for the potential energy of Ni-Al alloys based on the Embedded Atom Method. The potential is applied in a Molecular Dynamics and Quasi Harmonic investigation of the Martensitic Transformation (MT) that occurs in Ni x Al1− x for compositions 0.61<x<0.64 at a temperatureT M ranging from ~ 0 K atx=0.61 to ~ 400 K atx=0.64. We determine the transition temperature as a function of composition and pressure and we show that our potential reliably reproduces the known properties of the alloy.
We exploit the model to investigate the microscopic dynamical properties underlying the transition. Our computation shows that in the austenite the compositional disorder induces several bands of localized phonons, that discontinuously de-localize at the MT. We show that specific localized modes associated with Ni-rich clusters identify regions of incipient lattice instability, and provide favourable sites for the nucleation.
Sommario
L'articolo discute un modello ‘Embedded Atom’ per l'energia potenziale di leghe Ni-Al. Il potenziale viene utilizzato in uno studio di Dinamica Molecolare e nell'approssimazione Quasi Armonica della Transformazione Martensitica (MT) che ha luogo in Ni x Al1−x per 0.61<x<0.64 a una temperatutaT M compresa tra ~ 0 K perx=0.61 e ~ 400 K perx=0.64. La temperature di transizione è determinata in funzione della composizione e della pressione. I risultati dimostrano la validità del potenziale nel riprodurre le proprietà note della lega.
Il modello viene utilizzato per studiare la dinamica microscopica alla base della trasformazione. Lo studio mostra che nella austenite il disordine chimico legato alla non-stechiometria induce bande di fononi localizzati che si delocalizzano in modo discontinue allaMT. Viene mostrato che i modi localizzati sono associati a regioni rieche di Ni ed individuano siti di incipiente instabilità reticolare. Tali siti forniscono centri preferenziali per la nucleazione.
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References
Cohen, M., Olson, G. B., and Clapp, P. C. ‘On the classification of displacive phase transformation’ inICOMAT 79, MIT Press, Cambridge, MA, USA, 1979, pp. 1–11.
E. Hornbogen and N. Jost, (eds),The Martensitic Transformation in Science and Technology, DMC Informationgesellshaft Verlag, Overnosel, Germany, 1989.
Rubini, S. and Ballone, P., ‘Quasiharmonic and molecular-dynamics study of the martensitic transformation in Ni-Al alloys’,Phys. Rev. B 48 (1993), 99–111.
Rubini, S. and Ballone, P., ‘Phonon localization and martensitic transformation in Ni x Al1−x alloys’,Phys. Rev.,B 50 (1994), 1297–1300.
M. S. Daw and M. I. Baskes, ‘Semiempirical, quantum mechanical calculation of hydrogen embrittelment in metals’,Phys. Rev. Lett.,50 (1983), 1285–1288.
Foiles S. M. and Daw, M. S., ‘Application of the embedded atom method to Ni3Al’,J. Mater. Res.,2 (1987), 5–15.
Clementi, E. and Roetti, C., ‘Roothaan-Hartree-Fock atomic wavefunctions’,At. Data Nucl. Tables,14 (1974), 177–478.
Parrinello, M. and Rahman, A., ‘Polymorphic transitions in single crystals: A new molecular dynamics method’,J. Appl. Phys.,52 (1981), 7182–7190.
Bain, E. C.,Trans. AIME 70 (1924), 25.
Clapp, P. C., ‘The critical role of defects in first-order displacive transformations’,Mater. Sci. Eng.,A127 (1990), 189–195.
Clapp, P. C.,Phys. Stat. Sol., (b)57, (1973), 561.
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Rubini, S., Ballone, P. Martensitic transformation and phonon localization in Ni-Al alloys by atomistic simulations. Meccanica 30, 439–448 (1995). https://doi.org/10.1007/BF01557076
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DOI: https://doi.org/10.1007/BF01557076