The deformation behavior and mechanism modeling of a corrosion-resistant Ni-Cr-Mo alloy with nanoscale precipitates at room and elevated temperatures

Abstract

Ni-Cr-Mo alloys are widely-used materials in various critical applications owing to their excellent balance of strength and ductility. The precipitates play a significant role in the exceptional mechanical properties of these alloys, yet the precise microscopic mechanisms underpinning the enhanced properties are still open. Here, the atomistic simulation based on molecular dynamics (MD) was employed to investigate the deformation behavior and mechanism of the precipitation-strengthened single crystal Ni-Cr-Mo alloy under uniaxial loading at temperatures of 300K, 500K, 700K, and 900K. The results revealed high temperature-induced softening under both tension and compression. Furthermore, the tension-compression asymmetry in ultimate strength is influenced by the disparity in Schmid factor of leading Shockley partial dislocations. By monitoring the evolution of microscopic defects during deformation, the Shockley partial dislocation slip was identified as the primary deformation mechanism in the plastic regime at 300K, 500K, 700K, and 900K. Based on that, a flow stress representation model was proposed. Moreover, the investigation on the nanoscale Ni2(Cr, Mo) precipitates revealed the transition from the Orowan bypass mechanism to the shearing mechanism under uniaxial loading, accompanied by the formation of dislocation tangles. The dislocation tangles impeded dislocation slip, enhancing the mechanical properties of the alloy. The precipitate can significantly promote the formation of the lamellar dislocation structure under compression at 900K.