Microstructural Characterization and Mechanical Properties of Fiber Laser Welded CP-Ti and Ti-6Al-4V Similar and Dissimilar Joints

Abstract

In this research, the microstructures and mechanical properties of similar and dissimilar autogenous joints of 3 mm thick commercially pure titanium (CP-Ti) and Ti-6Al-4V welded by ytterbium fiber laser (Yb:YAG) were investigated. Two sets of laser power and welding speed were selected in such a way that the heat input remained constant. Microstructural characterization of the joints was investigated by an optical microscope, and mechanical properties were determined by hardness and tensile tests. The only defects found were porosity and underfill, and no signs of lack of penetration and solidification cracks were observed in any of the joints. Microstructural evaluation of the fusion zone (FZ) showed that in similar Ti-6Al-4V joint, a supersaturated nonequilibrium α′ martensite was formed due to rapid cooling associated with laser welding. In similar CP-Ti, coarse equiaxed grains were observed in the FZ. Unlike the similar joints, a clear interface was observed between the heat-affected zone (HAZ) and the FZ in both the CP-Ti and Ti-6Al-4V sides in dissimilar joints. Among all the joints with different weld parameters, similar Ti-6Al-4V showed the highest strength and the lowest ductility. In similar CP-Ti and dissimilar joints, fractures took place in the CP-Ti base metal, but all the Ti-6Al-4V similar joints failed in the FZ. Significant changes in the strength and hardness with varying laser power and welding speed implied that the mechanical properties of the weld fusion zones were not entirely governed by the heat input but were also affected by individual welding parameters.

Fatigue Improvement of Additive Manufactured Ti–TiB Material through Shot Peening

“…Tensile testing results highlighted that samples had sustained ductility in all directions measured through percent elongation and percent reduction in area, with average values of 8.9 ± 1.1% and 8.0 ± 1.2%, respectively, as presented in Table 2. This compares well with similar additive manufacturing processes involving commercially pure Ti [35,36], where a slight improvement in tensile strength is noted in this work with conserved ductility. Directionality of TiB particles can play a role in the strengthening effect of these additions within TMCs, where TiB behaves as discontinuous fibres within Ti alloys [15,34].…”

Welded Construction Design of Transition Fittings from Metal Pipes to Plastic Pipes

“…Metals and plastics are widely used in industrial applications, and the connection of a metal part with a plastic part is often necessary and important from a manufacturing point of view. Therefore, the combination of a metal material and a laser-assisted plastic material (LAMP) has been developed as an innovative direct laser joint, without adhesives or glue [1,2]. It has been demonstrated that the joining of metal and plastic materials through LAMP technology offers a high-strength nanostructural bonding through formation of an oxide film that has high reliability in various practical uses [3][4][5].…”

Titanium Alloys: Processing and Properties

“…Elements of fundamental metallurgy and microstructural evolution are described for highly specialised titanium-based laser welded joints, shape memory alloys, additive manufactured parts and biomedical Ti-Ni alloys (Abdollahi et al [2], Huang et al [3], Panin et al [4], Cascadan and Grandini [5], respectively). Choe et al [6] describe grain boundary TiFe precipitation in a α + β alloy and the employment of isothermal aging as a mechanism for controlling subsequent strength.…”