In-situ study of OFHC copper under low-cycle fatigue with different heat treatments at elevated temperature for fusion application

As the UK advances in fusion energy development, particularly with the European DEMOnstration Fusion Power Plant (DEMO), ensuring the structural integrity of materials in reactor components are becoming increasingly important. Oxygen-Free High Conductivity (OFHC) copper, used as an interlayer between tungsten and copper-based alloys, is a key candidate material for heat sinks in the divertor structural components. These materials are exposed to cyclic loading due to the repetitive nature of tokamak operations, making fatigue a significant concern for long-term reliability. The overarching aim of this research is to support the validation of structural integrity codes, such as the Structural Design Criteria for In-vessel Components (SDC-IC) which is derived from the RCC-MRx design code, and essential for ensuring the safe operation of fusion reactors. To achieve this, we aim to perform in-situ low-cycle fatigue tests on OFHC copper. The behaviour of the material under cyclic fatigue conditions will be evaluated at 400°C, representative of DEMO's operating temperature. Using the neutron diffraction technique, we will measure orthogonal strain components during the fatigue tests. These measurements will be used to validate crystal plasticity models by analyzing the evolution of lattice strain, under low-cycle fatigue conditions. This research will enhance the robustness of structural integrity codes in fusion energy applications.