Hot deformation behavior of Nb-contained 316LN was investigated using a series of compression tests performed on a Gleeble-1500D simulator at temperature of 950–1200 °C and strain rate of 0.01~1 s−1. Based on the strain compensation method, a modified Arrhenius constitutive model considering the comprehensive effects of temperature, strain rate, and strain on flow stress was established, and the accuracy of the proposed model was evaluated by introducing correlation coefficient (R) and average relative error (AARE). The values of R and AARE were calculated as 0.995 and 4.48%, respectively, proving that the modified model has a high accuracy in predicting the flow stress of Nb-contained 316LN. The microstructure evolution and the dynamic recrystallization (DRX) mechanism of the experimental material were explicated by optical microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscopy (TEM). It was found that continuous dynamic recrystallization (CDRX) characterized by subgrain evolution and discontinuous dynamic recrystallization (DDRX) featured by grain boundary nuclei are two main dynamic recrystallization (DRX) mechanisms of Nb-contained 316LN. Furthermore, based on the results of microstructure analyses, optimum parameters were obtained as temperature ranges of 1100~1200 °C and strain rate ranges of 0.01~1 s−1.

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The behavior of void surface healing in 316LN steel samples undergoing thermal plasticity deformation was investigated using the Gleeble 1500 thermomechanical simulator. The characterization of the void surface after plastic deformation was analyzed under different deformation temperatures, deformation amounts, and holding time durations. The morphology evolution and microstructure of the void surface healing zone during thermal plasticity deformation and holding time duration stage were analyzed using electron back scatter diffraction imaging. The mechanism of void surface healing under thermal plasticity deformation was investigated. It was found that the degree of void surface healing increases with the degree of deformation and the duration of the holding time. Dynamic recrystallization occurred continuously at the void surface, resulting in a plethora of crystal defects and a substantial amount of energy. These conditions were conducive to atomic diffusion and migration, thereby promoting the healing process of the void surface. Maintaining high temperature after deformation can continue to provide energy for the diffusion and migration of atoms, promotes the growth of recrystallized grains, and gradually heals the void surface.