Influence of grain size and precipitation hardening on high cycle fatigue performance of CuNiSi alloys

The objective of this study was to examine the influence of grain refinement on fatigue performance of Cu-2.5Ni-0.5Si-0.06Mg alloy (hereinafter referred to as CuNi3Si1Mg). The results indicate that the fatigue strength of the ultrafine-grained (UFG) CuNi3Si1Mg is about 1.6 times higher than the fatigue strength of the coarse-grained (CG) CuNi3Si1Mg. A detailed investigation of the fracture surfaces using scanning electron microscopy (SEM) showed that the initial microstructure affects the fatigue crack nucleation mechanism. In CG CuNi3Si1Mg, the cracks originated from the activated slip bands, while in UFG CuNi3Si1Mg, the cracks nucleated from the slip bands and twin boundaries.