Modeling of dislocation properties in Fe40Cr25Ni35 and Fe50Cr20Ni30 systems

TP Kaloni and A Prudil and DE Spearot and E Torres, NUCLEAR ENGINEERING AND DESIGN, 411, 112422 (2023).

DOI: 10.1016/j.nucengdes.2023.112422

Steels are used extensively in many industries due to their excellent balance of mechanical strength, manufac-turability, costs, and acceptable corrosion resistance. Steels are being considered for structural components that are exposed to particularly challenging environments in advanced nuclear reactors. In this context, force-field molecular dynamics (MD) simulations were performed on austenitic steel surrogates with Fe40Cr25Ni35 and Fe50Cr20Ni30 compositions to compute the lattice parameter, elastic constants, bulk modulus, Poisson ratio, the dislocation velocity as a function of shear stress, and the phonon drag coefficient for use in discrete dislocation dynamics (DDD) simulations. The accurate computation of these parameters is essential to obtain correct results by the evolution of the dislocation network of the materials using DDD simulations. The dislocation velocity was extracted from the MD calculations for both steel compositions at 30 different values of stress. Because no significant migration of dislocations was observed at stresses below 200 MPa, the dislocation velocity and mobility were calculated at stresses of 200 MPa and higher. Subsequently, the dislocation density and strain- stress relationship were then computed using the DDD approach. The elastic and plastic deformations in the Fe40Cr25Ni35 system were found to be considerably larger than those of the Fe50Cr20Ni30 system. Our study illustrates the ability of atomistic and dislocation dynamics simulations to elucidate qualitative descriptions of the elasticity and plasticity in steel materials, and thus can assist experimental efforts to evaluate the impact of deformation in austenitic steels.

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