Microstructural and Corrosion Properties of Ti-to-Zr Dissimilar Alloy Joints Brazed with a Zr-Ti-Cu-Ni Amorphous Filler Alloy

Abstract

Titanium and Zircaloy-4 dissimilar alloys were brazed with a zirconium-titanium-copper-nickel amorphous filler alloy, and the resulting joint structures as well as their corrosion properties were examined. The microstructure of the brazed joints was investigated according to brazing holding time at 850 °C, and the corrosion property was analyzed by potentiodynamic polarization. During brazing, joints were produced by diffusion-induced isothermal solidification of the molten filler alloy. At a relatively brief brazing holding time of 5 min, a large segregation zone consisting of an active α-phase and a nobler intermetallic phase was generated in the joint center, which suffered from micro-galvanic corrosion. The presence of alloyed titanium deteriorated the nobility of the α-zirconium phase near the joint and induced galvanic coupling with cathodic base metals, resulting in massive localized corrosion. This localized corrosion caused the pitting behavior at the applied potential of −51.1~187.5 mV during anodic polarization. With a brazing holding time of 20 min, the concentration of the alloying elements was homogenized to eliminate the electrochemical potential difference and minimize the galvanic corrosion susceptibility of the joint region. This homogeneous joint resulted in a highly passive corrosion behavior comparable to that of the titanium base metal.

Glass-Forming Ability and Corrosion Behavior of Ti-Based Amorphous Alloy Ti-Zr-Si-Fe

“…Compared with crystalline Ti-based alloys, amorphous titanium alloys exhibit higher mechanical properties [ 10 , 11 ], low elastic modulus, excellent biocompatibility and high corrosion resistance. With the development of titanium-based amorphous alloys, Ti-rich bulk glassy alloys were found in rapidly solidified Ti-Cu-Al [ 12 , 13 ], Ti-Cu-Ni (Co) [ 14 , 15 , 16 ], Ti-Cu-Zr-Ni [ 17 , 18 ], Ti-Cu-Co-Al-Zr [ 19 ] and Ti-Cu-Ni-Sn (Si) [ 20 , 21 ] systems to date. Since 1988, many alloys with high glass-forming ability and capable of being formed into bulk metallic glasses (BMG) have been discovered more and more, for example, in multicomponent Mg-, La-, Zr-, Fe- and Pd-based metals in the alloy system.…”

Influence of Zirconium on the Corrosion Passivation of Titanium in Simulated Body Fluid

“…Furthermore, adding Zr to Ti provides good biocompatibility, high mechanical strengths, and excellent corrosion resistance [12]. In this regard, many researchers have report the rule of Zr in improving the corrosion resistance as well as the biocompatibility of Ti [11][12][13][14][15]. As an example, Akimoto et al [13] studied the effect of different additions of Zr; namely, 30%, 50%, and 70%, on the corrosion of Ti in lactic acid containing sodium chloride solution and found that 30% Zr and at a Zr < 50% offer an ideal level of corrosion resistance for clinical applications.…”