Mechanism of self-healing behavior in rolled Cu-2Be flat product

Abstract

In this research, we aimed to investigate the self-healing behavior of Cu-2Be alloy (UNS C17200), which is used as a non-magnetic high-strength material, under various loading conditions, both static and dynamic, including tension-annealing and fatigue tests. We observed crack filling in all heat-treated and tested samples, specifically those subjected to solution heat treatment at 800 °C, under-aged (UA) conditions, and aging conditions at 320 °C for 5 and 30 min.The latter two phenomena were triggered by the precipitation of γ (CuBe) and γ’ phases after straining and heat treatment. The synergistic effect of dynamic aging and dislocation recovery resulted in increased ductility in the pre-strained and UA sample, as evidenced by post-fracture elongation, compared to specimens elongated up to a certain pre-strained level followed by annealing and aging. In conclusion, uniaxial fatigue testing revealed that the lifetime of UA Cu-2Be samples surpasses that of annealed and fully aged ones due to the efficient preparation of self-healing effects brought about by the precipitation of intermediate and final age-hardening phases, dislocation rearrangement, and grain boundary reinforcement through beryllium atoms. To characterize the precipitated CuBe, we conducted XRD, XPS, and DIGE phase identification analyses, alongside relevant electron microscopy analyses. Additionally, we investigated the possibility of crack closure by integrating the findings from the positron annihilation lifetime spectroscopy and coincidence Doppler broadening spectroscopy outputs, thus validating the results of spectroscopy and diffraction.