Mechanical and corrosion properties of Ti-6Al-4V alloy joints brazed with a low-melting-point 62.7Zr-11.0Ti-13.2Cu-9.8Ni-3.3Be amorphous filler metal

Highly reliable and sound Ti-6Al-4V joints were brazed at relatively low-temperatures below 820 degrees C by employing a 62.7Zr-11.0Ti-13.2Cu-9.8Ni-3.3Be (wt.%) bulk metallic glass alloy as a filler. The joint structures were controlled through the isothermal solidification in such a way that the segregated brittle phase, i.e., typically [Ti,(Zr)](2)(Cu,Ni) intermetallic phase, could be eliminated by forming the acicular Ti-rich grains throughout the microstructure. The strengths of the brazed joints were considerably high enough to induce either yielding or fracture in the base alloy, exceeding that of the bulk Ti-6Al-4V (similar to 950 MPa). The potentiodynamic polarization test in sea water revealed that the continuously segregated phase in the central region was mostly corroded owing to a severe galvanic attack. According to the impedance spectroscopy, the polarization resistance of the joint without the segregated phase showed a dramatic increase of up to 100,000 Omega cm(2) when compared with the bulk Ti-6Al-4V (55,600 Omega cm(2)). (C) 2013 Elsevier Inc. All rights reserved.