Comparative in-situ electron irradiation study on void swelling in mechanically alloyed and oxide dispersion strengthened coppers

The irradiation-induced swelling behaviour of oxide dispersion strengthened copper alloys was comparatively investigated by in-situ high-voltage electron microscopy under 1250 keV electron irradiation at 573 K. ODS-Cu, Zr-containing ODS-Cu (ODS-CuZr), annealed high-purity Cu, and mechanically alloyed Cu (MA-Cu) were examined to elucidate the role of microstructural defect sinks on void evolution. ODS-CuZr exhibited the highest swelling resistance, characterized by an extended incubation period, significantly reduced void size and number density, and an extremely low swelling rate. This enhanced performance is attributed to the high density of ultrafine Zr-containing oxide dispersoids, which act as sinks for irradiation-induced point defects and effectively increase the recombination and annihilation of interstitials and vacancies. In contrast, ODS-Cu showed earlier void nucleation and higher swelling than ODS-CuZr, while annealed Cu exhibited immediate void nucleation followed by void growth and coarsening due to its low sink quantity. MA-Cu displayed the most severe swelling behaviour, characterized by a high swelling rate and the absence of an incubation period due to the dense pre-existing nanocavities introduced during mechanical alloying. Combined with previous studies, a hierarchy of swelling resistance, ODS-CuZr > ODS-Cu > annealed Cu ≫ MA-Cu, can be summarised in the presented study. The findings highlight the effectiveness of Zr-containing dispersoids in enhancing the irradiation tolerance of Cu alloys.