Multi-scale modelling of plasticity in W-Mo-Nb ternary refractory alloys over broad temperature range
Final Report Abstract
Refractory metals play an important role in materials science and engineering, especially for high temperature applications. One of the most important characteristics of refractory alloys (RAs) is their peculiar, strongly temperature-dependent plasticity. Despite the numerous engineering applications, theoretical understanding and description of RA plasticity over broad range of temperatures is still under active discussion. This project aims to develop a plasticity model that can describe and predict the mechanical behaviour of refractory metals and alloys without empirical fitting to experimental data. There are four main achievements of this project: (1) development of new classical interatomic potential for W-Mo-Nb based only on DFT calculations, (2) study of diffusion characteristics in pure metals and alloys including a pipe dislocation diffusion, (3) calculation of dislocation mobility as a function of temperature and stress in pure metals and complex alloys, (4) calculation of the temperature dependence of flow stress and activation volume for pure metals (Nb, Mo, W) and complex alloys (Nb-25Mo, W-28Mo, WMoNb). The developed interatomic potential can reproduce many important properties of pure metals and complex concentrated alloys with good accuracy. The published works provided detailed validation of this potential and comparison with 5 available interatomic models of refractory alloys (both classical and machine learning models). The performed validation proves the high transferability of the developed potential. In particular, the applicability of the developed model is demonstrated by studying the diffusion coefficient of atoms in dilute and complex refractory alloys. Using large-scale atomistic simulation, the dislocation velocities were calculated for both athermal and thermally activated regimes. The study revealed a strong non-Arrhenius temperature behaviour of the screw dislocation mobility, especially for complex alloys. It was shown that accurate calculation of the dislocation mobility function makes it possible to predict with sufficient accuracy the measured plasticity characteristics in a wide temperature range. The characteristics calculated in the work are in good agreement with measurement data at temperatures above 150-200 K for Nb, Mo and Nb-25Mo alloys. For W, good agreement was obtained at temperatures above 400 K. On the other hand, the flow stress at zero temperature is close to the DFT predictions. Thus, the calculation of the mobility functions in large-scale simulations allows the measured properties at finite temperatures to be reconciled with the ab-inito calculation at zero temperature. Also, the proposed approach reproduces the existence of a temperature-independent plateau in the dependence of the flow stress on temperature for complex concentrated alloys.
Publications
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Optimized interatomic potential for atomistic simulation of Zr-Nb alloy. Computational Materials Science, 197, 110581.
Starikov, S. & Smirnova, D.
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Atomistic simulations of pipe diffusion in bcc transition metals. Acta Materialia, 260, 119294.
Starikov, Sergei; Jamebozorgi, Vahid; Smirnova, Daria; Drautz, Ralf & Mrovec, Matous
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Disordering complexion transition of grain boundaries in bcc metals: Insights from atomistic simulations. Acta Materialia, 261, 119399.
Starikov, S.; Abbass, A.; Drautz, R. & Mrovec, M.
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Angular-dependent interatomic potential for large-scale atomistic simulation of W-Mo-Nb ternary alloys. Computational Materials Science, 233, 112734.
Starikov, Sergei; Grigorev, Petr & Olsson, Pär A.T.
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Large-scale atomistic simulation of diffusion in refractory metals and alloys. Physical Review Materials, 8(4).
Starikov, Sergei; Grigorev, Petr; Drautz, Ralf & Divinski, Sergiy V.
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Dislocation mobility function as a key to understanding plasticity of refractory metals and alloys. Computational Materials Science, 246, 113411.
Starikov, S.
