Brazing TC4 titanium alloy/316L stainless steel joint with Ti50-xZrxCu39Ni11 amorphous filler metals

TC4 titanium alloy was brazed to 316L stainless steel with newly designed TixZr50-xCu39Ni11 amorphous filler metals. The effect of Zr content on the wettability of filler metals, interfacial microstructure and shear strength of the brazed joints was investigated. Precipitation behavior of submicron phase and fracture behavior of the brazed joints were analyzed. Increasing Zr content in filler metals first increased and then decreased the spreading area of filler metals on both TC4 titanium alloy and 316L steel substrates, and changed the primary phase in filler drops. Besides, residual filler metal layer was thickened due to the reduction of filler metal flowability. But the thickness of the transition zone decreased, particularly the alpha-Fe reaction layer, attributed to the attenuation of Ti diffusion from filler metal to 316L steel substrate. Submicron beta-Ti phase precipitated near the FeTi/Fe2Ti interface, and there were orientation relationships among the submicron beta-Ti phase, FeTi and Fe2Ti as follows: (110 )(FeTi)parallel to(110)(beta-Ti)/[1(_)11](FeTi)parallel to[1(_)11](beta-Ti) and (100)(FeTi parallel to)(100)(beta-Ti)/[001](FeTi)parallel to[011](beta-Ti). The shear strength of brazed joints first increased and then decreased with the peak value of 238 MPa at 22.2 at.% Zr. Stress concentration at FeTi/Fe2Ti interface and impossible orientation relationship between FeTi and Fe2Ti phases resulted in the brittle fracture at FeTi/Fe2Ti interface of the brazed joint. (C) 2020 Elsevier B.V. All rights reserved.