Specific very high cycle fatigue fracture mechanism in C17200 beryllium copper alloy caused by grain boundary precipitates and persistent slip bands

The damage behavior of C17200 beryllium copper alloy during very high cycle fatigue (VHCF) at a loading frequency of 20 kHz was investigated. Samples subjected to varying loading were characterized and evaluated to clarify the impact of internal microstructure on VHCF performance. The findings demonstrate that grain boundary precipitates (GBPs) significantly influence the VHCF fracture behavior of the C17200 alloy. GBPs facilitate a change in fracture mode from the crack initiation phase to the crack propagation phase. The interaction between GBPs-persistent slip bands (PSBs) created a distinctive phenomenon in the crack initiation phase, wherein cracks originate from the GBPs and propagate along the PSBs. Furthermore, it was verified that areas with a high density of precipitates lead to their detachment. This study introduces the inaugural examination of the VHCF performance and fracture process of C17200 alloy. A novel fatigue life prediction model, which integrates the impact of precipitates as a critical factor, was established, demonstrating strong concordance with experimental results.