Effect of 0.40 % and 0.20 % Titanium Addition on Microstructure Properties and Corrosion Behavior of CuAl10Ni5Fe4 Alloy

Abstract

This study examined how post-casting heat treatment (solution treatment and tempering) and forging affected the corrosion and microstructural properties of the nickel aluminium bronze (CuAl₁₀Ni₅Fe₄) with 0.20 % and 0.40% titanium addition. Heat-treated CuAl₁₀Ni₅Fe₄ alloy microstructures showed copper-rich α-solid solution, martensitic β-phase, and intermetallic κ-phases, such as flake-shaped κI, fine κIII, and black globular κIV. Adding 0.20 % and 0.40 % titanium to CuAl₁₀Ni₅Fe₄ alloys reduced dendritic arm thickness and increased κ phase abundance. Additionally, significant κIV and κII precipitations were observed in the tempered β phase. Tempering β may cause martensitic β to split into tiny α and κIII phases. The grain refinement of the CuAl₁₀Ni₅Fe₄, CuAl₁₀Ni₅Fe₄-0.20 % Ti, and CuAl₁₀Ni₅Fe₄-0.40 % Ti alloys was significantly noticeable after forging. The alloys retained the same α, β, and κ phases seen in the heat-treated alloys after forging. Titanium's refining effect increased the hardness of the alloy into which it was incorporated. Increased stiff phases, such as tempered β and fine κIV, contribute to increased hardness. The forging process enhanced the hardness of all three alloys. Forged and heat treated CuAl₁₀Ni₅Fe₄-0.40 % Ti alloy had the highest hardness with 243.50 HB and 256.18 HB, respectively. The microstructural phases α, β, and κ significantly impact the corrosion behaviour of CuAl₁₀Ni₅Fe₄ alloy. The CuAl₁₀Ni₅Fe₄-0.40 % Ti alloy after forging had the lowest 24-hour weight loss of 0.003326 mg/dm². The CuAl₁₀Ni₅Fe₄ alloy loses the most weight (0.013659 mg/dm²) following heat treatment (S.T.+T) after 24 hours. The minimal corrosion rate for the CuAl₁₀Ni₅Fe₄-0.40 % Ti alloy after forging was 0.003916 mg/(dm²·day) after 72 hours. Due to stratification, corrosion creates craters. Pitted or porous structures and craters are common. All alloys show a decrease in these structures after forging. The formation of the CuCl₂ phase is believed to occur in regions experiencing pitting corrosion.