EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Functionally Graded Materials (FGM) are materials whose composition, and hence properties, vary gradually throughout the material. These materials are commonly used as thermal barrier coatings without thermal stresses when they are required to ensure the structural integrity of components. Graded W/Cu materials, are potential candidates for the joining of the tungsten monoblocks plasma-facing material to the Cu-based cooling system of the future EU-DEMO reactor.

This FGM would replace the thick copper interlayer with a W/Cu compositionally graded thin film, fabricated by Cold-Spray with Cu and with an increasing W content from 0 to 75 vol.%W. In previous work, the properties of the free-standing coatings were studied, as well as their tensile behaviour. The results revealed that the addition of 75 vol%W increased the ultimate tensile strength by more than 50%, since the W acted as strengthening mechanism, halting the cracks generated.

In this paper, the adhesion between W-Cu was evaluated by performing in situ tensile tests of the FGM joints at different temperatures (RT to 600ºC). A micro-tensile testing machine was used for this purpose, and the DIC (Digital Image Correlation) technique was used to evaluate the real deformation suffered by the samples. The evolution of the microstructure and the deformation behaviour of the FGM joints were also observed.