Brazing of alumina dispersion strengthened copper alloy for fusion applications

Alumina dispersion strengthened copper alloys have been proposed as potential candidate structural materials for components in the Tokamak fusion reactors. However, successful application of these alloys is highly dependent on the ability to join the alloy to itself and other materials, such as stainless steel, during fabrication without destroying its superior properties. Great difficulties have been encountered when conventional brazing processes were used to joining dispersion strengthened copper alloys. Typically, these joints show low strength and poor ductility.; The investigation of the commercial low activation BCuP-3 braze alloy showed that braze joints with 335 MPa tensile strength compared with 452 MPa for the base metal were obtained by controlling braze holding time to 81 seconds using resistance heating. The embrittlement of the brazed joints was attributed to segregation of the alumina particles in a layer near the braze joint interface. A model describing the interaction between the solid/liquid interface and alumina particles during solidification of the braze joint was used to explain the phenomenon of particulate segregation in the joints.; A 66%Cu34%Mn braze alloy with low activation characteristics was developed to alter the interfacial reaction between the liquid filler metal and the alumina particles. High strength brazed joints (415 MPa tensile strength) of GlidCop Al-15 were produced using the 66%Cu34%Mn filler alloy in a vacuum and argon environments. The 66%Cu34%Mn filler alloy successfully eliminated the segregation of alumina particles at the braze interface. Tensile strengths of GlidCop Al-15 brazed joints made with 66%Cu34%Mn filler alloy at elevated temperatures were comparable to that of the base material. GlidCop Al-15 to 304 Stainless steel dissimilar metal brazed joints were produced using the 66%Cu34%Mn filler alloy under vacuum and argon environments. The dissimilar metal joints had relatively high tensile strength at room temperature (345 MPa for vacuum brazing, 333 MPa for argon brazing) and at elevated temperatures.