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An investigation on creep deformation and mechanical properties of a polycrystalline Fe-based alloy: a molecular dynamics study

Abstract:

In this work, Molecular dynamics (MD) simulation was carried out to uncover the mechanism of creep deformation in FeCrAl alloys. The MD results indicated that the rise in the amount of Cr and Al leads to the increase of creep rate in the samples. Moreover, under a constant temperature (1000 K) and alloying composition (FeCr15Al4), the increase of applied stress altered the creep mechanism from Coble mode to grain boundary sliding, followed by dislocation creep, which was accompanied with the appearance of tertiary creep stage in the strain-time curves. Considering the stress exponent values, it was found that the applied stress of 1-1.5 GPa is a transition value from Coble creep to dislocation creep. It was also unveiled that the atomic coordination number in the grain boundaries was averagely lower than the grain interiors, indicating that the boundaries were potential sites for the atomic motion and the defect nucleation. Finally, in comparison with the applied stress and temperature, the creep deformation is less sensitive to the alloying composition and grain size.