Influence of Deep Cryogenic Treatment on the Mechanical Properties and Corrosion Resistance of Nickel–Aluminum Bronze

The objective of this research is to enhance the mechanical and corrosion resistance properties of a cast Ni-Al bronze (NAB). To achieve this, the effect of deep cryogenic treatment (DCT), a process that has shown promise in other alloys, is initially investigated. It is demonstrated that, in the case of NAB, DCT induces only minor microstructural changes, which do not lead to any significant improvement in its properties. Consequently, it is proposed that a combined treatment be employed, involving annealing either before or after DCT. The results indicate that annealing at 675 °C for 2 h following cryogenic treatment at −180 °C increases the yield strength by approximately 11%. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in simulated seawater further confirm that this combination results in the formation of oxide layers with enhanced protective capacity. These improvements are attributed to the significant refinement and homogenization of the microstructure, including the globularization of the kI, kII, and, particularly, kIII phases, and an increase in the precipitation of the kIV phase in a finer and more homogeneous form within the alpha phase.