Fabrication of Tungsten-Vanadium Hybrid Material with Sufficient Toughness for High-Temperature Applications by Diffusion Bonding

The design of fusion plasma-facing components is challenging, as their materials have to meet rigorous requirements in terms of low activation and high-temperature strength. At the same time, sufficient ductility is required even in the low-temperature range. Unfortunately, these properties are not found in conventional materials. To solve this problem, a hybrid material that combines the high strength of one material with the high ductility of the other material was developed. This paper presents the hybrid material, which consists of thin tungsten and vanadium layers. This hybrid material was produced by means of diffusion bonding at relatively low temperature in a vacuum chamber. Microstructural investigations and nanoindentation tests indicated no cracks, no delamination, and no brittle intermetallic phases along the bond interfaces. Investigations of the mechanical properties of the hybrid material by instrumented Charpy impact tests revealed a relatively low ductile-to-brittle transition temperature (DBTT) at 124°C (compared to the DBTT of polycrystalline tungsten of >441°C) with an absorbed Charpy impact energy of 4.53 J [kleinst (KLST)-specimen]. Additionally, the tested Charpy impact specimens were found to be not fractured thoroughly even at room temperature.