Cyclic deformation and fatigue cracking behaviors of Cu–28wt%Ag binary alloy

Abstract

The cyclic deformation and fatigue cracking behaviors of coarse-grained Cu–28wt%Ag binary alloy were investigated under axial plastic strain amplitudes ranging from 10⁻⁴ to 7.5 × 10⁻⁴. It was found that the cyclic stress of the Cu–Ag alloy increased rapidly in the initial tens of cycles and became saturation with further cyclic deformation. The cyclic saturation stress increased with increasing the plastic strain amplitude. The interfaces are classified into two categories based on the orientations of the eutectic and the dendrites, i.e. type I and type II interfaces. The surface damage morphologies show that fatigue cracks normally nucleated either along the type I interfaces or along the slip bands (SBs), while no cracking occurred along the type II interface. Fatigue striations with different spacings appeared on the fracture surface, and secondary cracks along the striations were also observed. Based on the experimental results, the cyclic deformation and fatigue cracking behavior of the Cu–Ag binary alloy were discussed in detail.

Keywords:

• Cu–Ag alloy
• cyclic deformation
• slip bands
• fatigue cracking
• interphase interface
• fatigue striation

Acknowledgements

The authors thank Q.Q. Duan, P. Li, H.J. Yang, W. Gao, H.H. Su, J.L. Wen and G. Yao for sample preparation, mechanical tests and SEM observations. This work was financially supported by the “Hundred of Talents Project” of Chinese Academy of Sciences, and the National Natural Science Foundation of China (NSFC) under grant Nos. 50571104, 50625103 and 50890173.