Study on Mechanical Properties, Microstructure and Corrosion Behaviour of Cu-10Ni Alloy with Varying La Contents and Ageing Parameters

This study investigates the influence of lanthanum (La) microalloying and ageing treatment on the microstructural evolution, mechanical performance, and corrosion behaviour of Cu-10Ni alloys. Alloys containing 0, 0.1, 0.2, 0.3, and 1.5 wt.% La were prepared through an optimization process and aged at temperatures of 400, 450, and 500 °C for a constant duration of 4 hours. Characterization was then carried out using optical microscopy (OM), scanning electron microscopy (SEM), mechanical testing, and electrochemical polarization analysis. The results reveal that low-to-moderate La additions (0.1-0.3 wt.%) significantly refine the grain structure, purify grain boundaries, and promote the formation of uniformly distributed nanoscale La-rich precipitates. These microstructural modifications lead to substantial improvements in tensile strength, hardness, toughness, and corrosion resistance. The alloy containing 0.3 wt.% La aged at 450 °C exhibited the most favourable balance of properties, achieving a tensile strength of 542 MPa, hardness of 166.1 HBW, toughness of 78 J, and the lowest corrosion current density. Strengthening was governed by a synergistic combination of grain refinement, precipitation hardening, and Orowan looping. In contrast, excessive La addition (1.5 wt.%) and over-ageing at 500 °C resulted in precipitate coarsening, semi-continuous grain boundary phases, and degraded mechanical and electrochemical performance. Optimization results confirmed that Cu-10Ni-0.2La aged at 450 °C gives the most favourable balance of strength, toughness and corrosion resistance, whereas higher La levels yield limited strength gains but reduced overall performance. The combined experimental and ANFIS optimization findings demonstrate that controlled La microalloying in the range of 0.2 - 0.3 wt.% combined with ageing at is 450 °C gives the most favourable compromise between strength, toughness and corrosion resistance.