Fatigue behavior of precipitation strengthened Cu–Ni–Si alloy modified by Cr and Zr addition

Abstract

PurposeThe purpose of this paper is to investigate the fatigue behavior of precipitation-strengthened Cu‒2.55Ni‒0.55Si alloy, modified by the addition of 0.25 Cr and 0.25 Zr (wt%), using mechanical and fractographical studies to reveal the effect of microstructural features on the fracture.Design/methodology/approachFor strengthening, cast and hot forged alloy was subjected to solution annealing at 900°C for 60 min, followed by quenching in water and then aging at 490°C for 180 min. Precipitation-hardened alloy was exposed to fatigue tests atR=−1 and different stress levels. All fracture surfaces were examined within the frame of fractographical analysis.FindingsFine Ni-rich silicides responsible for the precipitation strengthening were observed within the matrix and their interactions with the dislocations at lower stress level resulted in localized shearing and fine striations. Although, by the addition of Cr and Zr, the matrix consisted of hard Ni, Zr-rich and Cr-rich silicides, these precipitates adversely affected the fatigue behavior acting as nucleation sites for cracks.Originality/valueThese findings contribute to the present knowledge by revealing the effect of microstructural features on the mechanical behavior of precipitation-hardened Cu‒Ni‒Si alloy modified by Cr and Zr addition.