Microstructure-dependent fatigue behavior of aged Cu-6Ni-1.5Si alloy with discontinuous/cellular precipitates

Abstract

The effect of microstructure on the fatigue strength of age-hardened Cu-6Ni-1.5Si alloy was investigated in this study. The aging was conducted at 500 degrees C for 0.5 h for the precipitation of disk-shaped delta-Ni2Si precipitates (continuous precipitates) and 3 h for the discontinuous precipitation of fiber-shaped, stable delta-Ni2Si precipitates to strengthen the Cu matrix. The tensile strength of 0.5 h-aged specimens was about 1.3 times greater than that of the 3 h-aged counterparts, but with inferior electrical conductivity. Despite the considerable difference in tensile strength, no notable difference in fatigue strength was observed between 0.5 h- and 3 h-aged specimens. The 3 h-aged specimens had superior electrical conductivity without sacrificing fatigue strength of the 0.5 h-aged specimens. The physical background of high-cycle fatigue strength in Cu-6Ni-1.5Si alloys with continuous precipitates and discontinuous precipitates is discussed considering the microstructure-sensitive behavior of fatigue cracks.