Corrosion and Mechanical Properties of Inconel 625 Alloy with Gradient Twin Structure Regulated via Interface Engineering

In this paper, solution-treated Inconel 625 alloy was selected as the research object. Combined with the low-energy characteristic of annealing twin boundaries and the synergistic strengthening effect of gradient structures, the alloy microstructure was tailored without altering its chemical composition. The evolution mechanism of grain size and twin boundary fraction, as well as their influence on corrosion resistance, were investigated. On this basis, the synergistic strengthening effect of gradient structure and interface regulation on the corrosion and mechanical performance of the alloy was further explored. The results show that a gradient-structured Inconel 625 alloy with abundant annealing twins and high-density grain boundaries can be fabricated by surface nanocrystallization combined with high-temperature short-time annealing. The variation in annealing twin fraction with grain size in interface-modified Inconel 625 complies with the Pande model. In terms of corrosion resistance, the microstructure consisting of fine grains and a high fraction of annealing twins exhibits superior performance compared to coarse grains with identical twin content. Its corrosion potential is tripled, while the corrosion current density is reduced by 11 times, delivering outstanding anti-corrosion capability in NaCl solution. Benefiting from the integrated merits of gradient architecture, annealing twins and fine grains, the interface-tailored Inconel 625 alloy achieves excellent comprehensive performance, with a yield strength of 925 MPa, elongation of 26%, and corrosion current density of 3.02 × 10−8 A/cm2, realizing the integration of high strength, good ductility and superior corrosion resistance for Inconel 625 alloy.