Effects of Grain Size and Temperature on the Tensile Properties of Nanocrystalline Fe–Mn Alloy

Abstract

This study investigates the effects of grain size and temperature on the tensile properties and deformation mechanisms of a body-centered cubic nanocrystalline Fe-Mn alloy using molecular dynamics simulations. Results indicate that Young's modulus increases with grain size, while the dominant deformation mechanism transitions from grain boundary (GB) migration to dislocation glide and stacking fault formation. The alloy exhibits Hall-Petch and inverse Hall-Petch behaviors with a critical grain size of ∼16.21 nm, which triggers large-scale intragranular twinning. Elevated temperatures reduce peak stress and Young's modulus by widening GBs and suppressing dislocation formation in favor of GB-mediated deformation. Furthermore, macroscopic tensile experiments on Q345R steel validate the simulated macro-mechanical responses and grain-refinement strengthening within the Hall-Petch regime. These findings provide a theoretical basis for the strengthening-toughening mechanisms and temperature-dependent design of nanocrystalline alloys.