Radiation-induced defects are first produced in the form of atomic scale point defects, vacancies and interstitials, which evolve into larger point defect clusters, such as dislocation loops, voids, and bubbles. Accumulation of these radiation defects degrades mechanical performance typically in the form of significant increases in hardening and embrittlement. Interface engineering is becoming a recognized and widely adopted method for designing radiation tolerant materials.
Recently, the research team led by Prof. Weizhong Han (韩卫忠) at the State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, uncovered defect-interface interactions in irradiated Cu/Ag nanocomposites, which was published in Acta Materialia (2018, 160:211-223).
In this work, we employ transmission electron microscopy and helium ion irradiation to study the response of biphase interfaces to radiation induced point defect fluxes from the two adjoining phases. Analysis of interface-affected defect accumulation was carried out over a wide range of radiation damage levels from near zero dpa to 16 dpa and helium concentrations of 0 at.% to 8 at.%. Results show a strong interface density dependence in which Cu/Ag interfaces in the nanolayered regions spaced < 500 nm were remarkably microstructural stable over the entire range without accumulating micro-scale defects, while those spaced > 1 m apart were destroyed. We report the concomitant development of a bubble-free zone in Cu that was independent of defect levels and interface-contacting bubbles zone in Ag. This finding is explained by bias segregation to the interface of interstitials from Ag and vacancies to misfit dislocation nodes in the interface from Cu. The point defect transfer across the interface can be explained by the spatial variation in interface pressure within the interface and gradient in pressure across the interface, both originating from the lattice mismatch and surface energy difference between the two crystals.
