Experimental and process modelling of chemical composition and thermal ageing of Ti-doped cast Cu-Ni alloy for microstructural, conductivity, and mechanical properties

Abstract

This study investigates the effects of titanium (Ti) content and thermal aging on the mechanical properties, microstructure, and electrical conductivity of Ti-doped Cu-10Ni alloy. Both as-cast and heat-treated alloys were subjected to comprehensive mechanical testing, electrical conductivity measurements, and microstructural analysis. A response surface methodology (RSM) was employed for statistical analysis, predictive modeling, and optimization, with Ti concentration (0.1–3.5 wt%) and aging temperature (400°C–500°C) as the independent variables, and tensile strength, elongation, hardness, impact strength, and electrical conductivity as response variables. The results indicate that Ti addition, particularly in the range of 1.5–3.5 wt%, refined the as-cast microstructure of Cu-10Ni alloys, leading to modest improvements in mechanical properties compared to the base alloy. Aging treatments promoted the formation of precipitates and second phases, notably β-Ni₃Ti, β-Ti₂, and δ-Ti₂Ni, which contributed significantly to property enhancement. The alloy's ultimate tensile strength (UTS) reached 659 MPa with 2.5 wt% Ti aged at 500°C for 2 h. At 3.5 wt% Ti and 450°C aging, the alloy exhibited the highest values for elongation (24.23 %), hardness (193.4 BHN), and impact strength (157 J). Electrical conductivity also improved across all Ti concentrations after aging, with conductivity increasing with higher aging temperatures, though the rate of increase diminished as Ti content rose. Statistical analysis demonstrated good agreement between experimental and predicted values, with the regression models being statistically significant (p < 0.05). Optimal alloy composition and aging conditions were identified, yielding the best combination of mechanical properties and electrical conductivity for the Cu-10Ni alloy.