The addition of Cu improves the corrosion resistance and plasticity of 316L stainless steel

This paper systematically investigates the effect of Cu addition on the microstructure, electrochemical corrosion resistance, and mechanical properties of 316L austenitic stainless steel. Microstructural characterization reveals that the grains in all tested samples are predominantly equiaxed. With increasing Cu content, the grain boundary density increases, and the austenite grains are significantly refined and become more uniform, with the average grain size decreasing from 34.21 μm to 4.84 μm. The grain size distribution gradually narrows from a wide span and concentrates in the smaller size range, while the frequency of grains in the larger size region decreases significantly. Kernel Average Misorientation (KAM) results are predominantly low-value, with higher KAM values mainly distributed near grain boundaries, indicating that local orientation fluctuations are primarily concentrated in the grain boundary regions. Electrochemical test results show that Cu addition shifts the corrosion potential in the positive direction, reduces the corrosion current density, and significantly increases the polarization resistance and charge transfer impedance. XPS results further confirm that Cu promotes the enrichment of protective Cr 2 O 3 and optimizes the compactness and chemical composition of the passive film. This suggests that the kinetics of the interfacial reaction are inhibited and the stability of the passive film is enhanced. Immersion weight loss results also demonstrate that Cu addition reduces the corrosion rate. The addition of Cu has a minor effect on strength but significantly enhances plasticity, with the elongation increasing from 47.42% to 60.12%. The mechanism of property evolution is further discussed from the perspectives of grain refinement and microstructural homogenization, the distribution of grain boundary-related local defects, and the combined effect of Cu on passivation behavior and strengthening mechanisms.