Thermal Cycling Stresses in W-Monofilament Reinforced Copper

• Published in: Advanced engineering materials 2011-08, Vol.13 (8), p.742-746
• Main Authors: Schöbel, Michael, Jonke, Johannes, Degischer, H. Peter, Herrmann, Aurelia, Brendel, Annegret, Wimpory, Robert, Buslaps, Thomas
• Format: Article
• Language: English
• Subjects: ADHESION; COMPOSITES; Copper; ETCHING; Fiber-matrix adhesion; HEAT SINKS; Metal matrix composites; Reactor design; REINFORCEMENT; STRESS; Stresses; THERMAL CYCLING
• ISSN: 1438-1656; 1527-2648; 1527-2648
• DOI: 10.1002/adem.201000309

New materials have to be developed for fusion reactor systems to withstand the high thermal load and heavy irradiation under service conditions. The divertor element collects the residuals of the nuclear reaction and withdraws heat from the reaction chamber into a heat sink. A thermal flux of ≈20 W mK−1 can be expected in such components. A plasma facing W plate is attached to a CuCrZr heat sink suffering CTE mismatch stresses at the interface due to pulsed operation required for the Tokamak reactor design. Fiber reinforced metal matrix composites are applied as an interlayer to reduce macroscopic interfacial stresses in these components. W‐wire reinforced copper is a promising material for this application due to a good fiber‐matrix bonding strength which is further increased by surface etching or graded interface designs. Thermal stresses in between the matrix and the wires are responsible for thermal fatigue damage within the constituents and at their interface. Neutron and synchrotron diffraction was performed in situ during thermal cycling to determine the micro stress amplitudes and their changes under simulated service conditions. W‐wire reinforced copper composites are developed as heat sink material for novel fusion reactor systems. High CTE‐mismatch stresses between the tungsten wires and the copper matrix lead to thermal fatigue damage under operation conditions. These stresses were measured by in situ neutron and synchrotron diffraction during thermal cycling. Both methods delivered similar results on the micro stresses, their direction and magnitude in a composite with a soft ductile matrix reinforced with stiff fibers during changing temperatures.