Abstract
Abstract Microstructural evolution and interfacial reactions during vacuum brazing of grade-2 Ti and 304L-type stainless steel (SS) using eutectic alloy Ag-28 wt pct Cu were investigated. A thin Ni-depleted zone of $$\alpha $$ α -Fe(Cr, Ni) solid solution formed on the SS-side of the braze zone (BZ). Cu from the braze alloy, in combination with the dissolved Fe and Ti from the base materials, formed a layer of ternary compound $$\tau _2$$ τ 2 , adjacent to Ti in the BZ. In addition, four binary intermetallic compounds, Cu $$_3$$ 3 Ti $$_2$$ 2 , Cu $$_4$$ 4 Ti $$_3$$ 3 , CuTi and CuTi $$_2$$ 2 formed as parallel contiguous layers in the BZ. The unreacted Ag solidified as islands within the layers of Cu $$_3$$ 3 Ti $$_2$$ 2 and Cu $$_4$$ 4 Ti $$_3$$ 3 . Formation of an amorphous phase at certain locations in the BZ could be revealed. The $$\beta $$ β -Ti(Cu) layer, formed due to diffusion of Cu into Ti-based material, transformed to an $$\alpha $$ α -Ti + CuTi $$_2$$ 2 eutectoid with lamellar morphology. Tensile test showed that the brazed joints had strength of 112 MPa and failed at the BZ. The possible sequence of events that led to the final microstructure and the mode of failure of these joints were delineated.
Highlights
TITANIUM and its alloys find applications in various sectors such as aerospace, chemical, biomedical, and nuclear due to their high strength to weight ratio and corrosion resistance properties.[1,2] The range of application of these materials, in combination with other structural materials, such as stainless steels (SS), is greatly enhanced by the appropriate selection of joining techniques
Dissimilar materials joints between stainless steel and titanium are widely used in the aerospace engineering, heat exchangers in chemical and petrochemical industries, sub-assemblies in nuclear reactors, and nuclear fuel reprocessing plants, in the dissolver assembly for reprocessing of spent nuclear fuel.[3,4,5,6,7]
The furnace was maintained at about 5 Â 10À5 mbar vacuum and the temperature of the sample was monitored with a thermocouple spot welded on the body of the Ti piece, close to the SS–Ti interface
Summary
TITANIUM and its alloys find applications in various sectors such as aerospace, chemical, biomedical, and nuclear due to their high strength to weight ratio and corrosion resistance properties.[1,2] The range of application of these materials, in combination with other structural materials, such as stainless steels (SS), is greatly enhanced by the appropriate selection of joining techniques. Dissimilar materials joints between stainless steel and titanium are widely used in the aerospace engineering, heat exchangers in chemical and petrochemical industries, sub-assemblies in nuclear reactors, and nuclear fuel reprocessing plants, in the dissolver assembly for reprocessing of spent nuclear fuel.[3,4,5,6,7] Brazing is widely employed in joining dissimilar materials.[8,9] The choice of vacuum brazing for joining Ti alloys and stainless steels, in preference to fusion welding, diffusion bonding, and explosion welding, is elaborated elsewhere.[10]. Given its importance in engineering applications, the brazing of Ti and its alloys with steels has been investigated quite extensively
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