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The joining of Ti6Al4V and Inconel 718 constitutes a great challenge, due to the TixNiy, Ti-Cr, and Ti-Fe brittle phases’ formation. For the solution of this problem, niobium was selected as an interlayer and the pulsed laser welding-induced eutectic reaction technology was proposed. Two metallurgical bonding zones based on two different bonding mechanisms were identified for the Ti6Al4V/Inconel718 dissimilar joint. When the laser beam was positioned at the Ti6Al4V/Nb interface, the Ti6Al4V and the Nb sheet were partially melted, for the Ti6Al4V and niobium to be joined through fusion welding, while the atomic interdiffusion and the eutectic reaction were responsible for the joining at the Nb/Inconel 718 interface. No TixNiy, Ti-Cr, or Ti-Fe intermetallics were detected in the weld, demonstrating that the unmelted Nb interlayer acted as a diffusion barrier between the Ti6Al4V and the Inconel 718. The eutectic reaction layer formed at the Nb/Inconel 718 interface with the main microstructure of the Ni-Nb system intermetallics. The welded joints fractured at the reaction layer at the maximum tensile strength of 145 MPa and the fracture mode was cleavage fracture. [ABSTRACT FROM AUTHOR]

The present paper studied the evolution of tensile damage in joints welded using laser beam welding (LBW) and gas tungsten arc welding (TIG) under a uniaxial tensile load. The damage evolution in the LBW joints and TIG-welded joints was studied by using digital image correlation (DIC) technology and monitoring changes in Young's modulus during tensile testing. To study the mechanism of void nucleation and growth in the LBW joints and TIG-welded joints, test specimens with various amounts of plastic deformation were analyzed using a scanning electron microscope (SEM). Compared with TIG-welded joints, LBW-welded joints have a finer microstructure and higher microhardness in the fusion zone. The SEM analysis and DIC test results indicated that the critical strain of void nucleation was greater in the LBW-welded joints than in the TIG-welded joints, while the growth rate of voids was lower in the LBW-welded joints than in the TIG-welded joints. Thus, the damage ratio in the LBW joints was lower than that in the TIG-welded joints during tensile testing. This can be due to the coarser martensitic α′ and the application of TC-1 welding rods in the TIG-welded joint. [ABSTRACT FROM AUTHOR]

In this study, the influence of weld cross-sectional profiles and microstructure, under different welding conditions, was investigated on the mechanical properties of pulsed Nd:YAG laser-welded joint of Ti6A14V alloy. The V- and H-shaped weld cross-section profiles were obtained under low and high heat input, respectively. The microstructure in the fusion zone (FZ) of V- and H-shaped welded joint consisted of a fine acicular martensitic α′ solidification structure within the prior-β grains, responsible for the maximum hardness in the FZ. Tensile tests revealed that the V-shaped welded joint fractured at the near heat-affected zone (HAZ)/base metal (BM) interface, but the H-shaped welded joint fractured in the BM. Furthermore, the tensile strength of the V-shaped welded joint was lower than that of the H-shaped welded joint. This was attributed to the fact that the heterogeneity of strain distribution at the interface of HAZ and BM of the V-shaped welded joint was greater than that of the H-shaped welded joint during tensile process. [ABSTRACT FROM AUTHOR]

Highlights: [•] The influence of the great microstructure gradient on fatigue damage behavior of Ti6Al4V LBW joint was studied. [•] The fatigue residual strength and fatigue crack growth rate of Ti6Al4V sheets and LBW joint were investigated comparably. [•] Effects of microstructure on fatigue fracture surfaces properties of Ti6Al4V sheets and LBW joint were analyzed comparably. [Copyright &y& Elsevier]