MICROSTRUCTURE AND FATIGUE PROPERTIES OF CU–NI–SI ALLOY STRENGTHENED BY NI2SI INTERMETALLIC COMPOUNDS

Abstract

Microstructure and fatigue properties of Cu–6Ni–1.5Si alloy having different morphologies of Ni2Si intermetallic compounds that are disk-shaped continuous precipitates (CPs) with nano-size diameter by normal aging, fibre-shaped discontinuous precipitates (DPs) by overaging and elongated DPs fabricated by cold-rolling (DPR) were studied. There was a negligible difference in fatigue strength between the CP and DP specimens despite higher tensile strength of the CP specimen. The DPR specimen had the highest tensile and fatigue strengths in all specimens. The fatigue crack initiation resistance of the DPR specimen was drastically enhanced. The growth rate of a small crack can be determined by a term σanl. The crack growth resistance of the DPR specimen was nearly equal to that of the CP specimen. The reason for such trends of tensile and fatigue strengths was discussed based on the microstructure of each specimen.