Fatigue behavior of Cu-6Ni-1.5Si alloy with discontinuous precipitates and the effect of difference in rolling before solution heat treatment

On Cu-Ni-Si alloy with high solute concentrations, overaging brings a decrease in strength because of formation of discontinuous precipitate (DP) phases. Recently, it has been shown that both electrical conductivity and tensile strength of mechanically deformed Cu-Ni-Si alloy with fully DP-structure were 1.3 times greater than those of conventional precipitate-strengthened Cu-Ni-Si counterparts. This throws a new light on the usage of DP phases. However, there are less studies on the fatigue behavior of DP phases. In addition, cold- and hot-rolling before solution heat treatment (SHT) are commonly conducted to eliminate defects in a casting slab and reduce the thickness of casting slab before SHT. However, the effect of rolling before SHT on the fatigue strength of DP-structure is unclear. In the present study, fatigue tests of Cu-6Ni-1.5Si alloy smooth specimens with DP-structure fabricated through different rolling processes before SHT were conducted. The fatigue strength, crack initiation and propagation behavior of DP-structure Cu-Ni-Si alloy were discussed.