Microstructure evolution of TC4 titanium alloy/316L stainless steel dissimilar joint vacuum-brazed with Ti-Zr-Cu amorphous filler metal
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TC4 titanium alloy was vacuum-brazed to 316L stainless steel (SS) with Ti-Zr-Cu amorphous filler metal. The effect of brazing time and temperature on the interfacial microstructure and mechanical properties of joints was investigated. Electron probe micro-analyzer (EPMA) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) were used to study the joint microstructure; meanwhile, the reaction phases on fracture surfaces were identified by X-ray diffraction (XRD). The results show that all joints had similar interfacial microstructure of TC4 titanium substrate/Widmanstätten/β-Ti + Ti2Cu/(α-Ti + λ-Cu2TiZr) + Ti2Cu/Ti-Fe-Cu/TiFe/(Fe, Cr)2Ti/σ-phase + Fess/316L stainless steel substrate. Three reaction layers TiFe/(Fe, Cr)2Ti/σ-phase + Fess formed close to 316L stainless steel substrate and could benefit the mechanical properties of joints. The maximum shear strength of 65 MPa was obtained at 950 °C for 10 min. During shear test, cracks initiated at the interface of Ti-Cu-Fe layer/TiFe layer and propagated along the brazed seam/316L interface with a large amount of cleavage facets existing on the fracture surface.
KeywordsVacuum brazing Ti-Zr-Cu amorphous filler metal Interfacial microstructure Intermetallic compound (IMC) Shear strength
The authors appreciate Professor Jian Cao at Harbin Institute of Technology in using a vacuum furnace. This work was technically supported by the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning.
This work was financially supported by the National Key Research and Development Program of China (Program No. 2016YFB0701401) and the National Natural Science Foundation of China (Nos. 51674060 and 51605075).
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