Effect of Ti addition on tensile properties of Cu-Ni-Si alloys

This study examines how varying Ni and Si contents and the addition of Ti affect the tensile behavior of Cu-Ni-Si alloys with different aging conditions. Cu-3Ni-0.7Si and Cu-6Ni-1.4Si alloys, both with and without the addition of Ti, were prepared by solution-heat treatment at 950 °C for 2 h, then aged at 500 °C for 1/ 6 h, 1/3 h, 1/2 h, 1 h, 3 h and 6 h, before tensile tests were conducted. Doubling the Ni and Si contents in Cu-Ni-Si alloys greatly increased the tensile strength and grain refinement, while marginally reducing the tensile elongation. Meanwhile, adding Ti to Cu-Ni-Si alloys reduced the grain size and greatly increased the tensile elongation. The aging response was also significantly accelerated by the addition of Ti. However, the expected improvement in tensile strength was not obtained by adding Ti, addition due to the agglomeration of coarse Ni₂Si precipitates and the accelerated lamellar structure formation. Finally, we discuss the microstructural changes that result from variations in aging time, different Ni and Si contents and the addition of Ti on Cu-Ni-Si alloys based on detailed optical, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographic observations and SEM fractographic analysis.