Effects of a Small Amount of Rare Earth La Addition on Microstructure and Corrosion Properties of As‐Cast Cu–Ni–Si Alloys

ABSTRACT The effects of La microalloying on the microstructure and corrosion behavior of as‐cast Cu–2.3Ni–0.6Si alloy in 3.5 wt.% NaCl solution were investigated through OM, XRD, SEM, EDS, and an electrochemical workstation. Results indicate that as the La content increased from 0.05 to 0.20 wt.%, the as‐cast microstructure of the alloy initially coarsens and subsequently refines. La not only aggregates near the Ni₂Si phase but also induces a preferred crystallographic orientation in in the Cu–2.3Ni–0.6Si alloy. Electrochemical corrosion results demonstrate that Cu–2.3Ni–0.6Si–0.05La exhibits optimal corrosion resistance in 3.5 wt.% NaCl solution, achieving the highest charge transfer resistance (1974 Ω·cm²), the maximum polarization resistance (292.31 kΩ·cm²), and the lowest corrosion current density (1.49 µA·cm⁻²). The improved corrosion resistance is attributed to the combined effects of La's purification role and its promotion of preferential growth of low‐index crystallographic planes with high planar density during solidification.