Tungsten-based bcc-superalloys: Thermal stability and ageing behaviour

Tungsten is considered as a primary material for the divertor and first wall in many fusion reactor designs. There has been further interest nano-structured multi-phase tungsten alloys composites, such oxide dispersion strengthened alloys, where interfaces may be harnessed defect sinks to improve irradiation resilience, whilst also improving base mechanical strength, potentially ductility. Here we investigate concept of tungsten-based ‘bcc-superalloys’ within W-Ti-Fe ternary system, comprising W-TiFe, A2-B2, β-β’ nanostructures. Alloys were produced by arc melting microstructure controlled via thermal heat treatments, solutionising at 1250 °C, followed 750 °C ageing. The characterised using electron microscopy, including composition measurements, alongside hardness measurements. Building on our previous work, have demonstrated that nano-scale B2 TiFe(W) forms A2(W,Ti,Fe) creating localised regions targeted A2-B2 (β-β’) precipitate reinforced structure. Further, here evaluated ageing interdendritic domains decomposition consistent with B2TiFe(W) -> + A2 A2(Ti,Fe,W) A3 proposed. An experimentally validated preliminary phase diagram produced, helping understand stable phases present instructing onward optimisation W-superalloys candidate energy.