Nowadays, there is a great manufacturing trend in producing higher quality net-shape components of challenging geometries. One of the major challenges faced by additive manufacturing (AM) is the residual stresses generated during AM part fabrication often leading to unacceptable distortions and degradation of mechanical properties. Therefore, gaining insight into residual strain/stress distribution is essential for ensuring acceptable quality and performance of high-tech AM parts. This research is aimed at comparing microstructure and residual stress built-up in Ti-6Al-4V AM components produced by Wire + Arc Additive Manufacturing (WAAM) and by laser cladding process (CLAD). 2 Introduction Additive manufacturing, often called 3D printing is nowadays among the most studied processes. AM is a key technique of a great potential in reducing high cost of producing conventional components made from relatively expensive materials such as titanium alloys. The worldwide Ti component production is constrained due to the high cost of Ti in comparison to other materials. Therefore, AM techniques aiming towards zero waste manufacturing are identified as potential prosperous routes in broadening Ti parts fabrication that are usually affected by often difficult and extensive machining. Ti is very broadly used in space, aerospace, nuclear, marine and chemical industries by virtue of its desirable properties such as high specific strength combined with excellent corrosion and oxidation resistance [1]. Although Ti is a very cherished material, its use in AM processes is also relatively challenging because of its low thermal conductivity which results in drawbacks such as uneven temperature field and poor interlamination integration [2]. Avoiding extensive machining by a near netshape successive layers fabrication can reduce the Ti parts production cost significantly. The buy-tofly ratio for a part machined from forged billet is typically 10-20 [3] and can potentially drop to nearly 1 when produced by AM techniques. There are numerous AM techniques that are capable of producing complex geometries close to their net-shape. Simply, AM techniques can be classified according to feeding technique, heat source or feedstock material. Powder bed, blown power and wire feed are the main AM techniques using heat sources such as electron beam, laser or electric arc, while the most common feedstock materials are powder or wire. Despite the similarity of AM

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Residual stress and distortion continue to be important issues in shipbuilding and are still subject to large amounts of research. This paper demonstrates how the type of welding process influences the amount of distortion. Many shipyards currently use submerged arc welding (SAW) as their welding process of choice. In this manuscript, the authors compare welds made by SAW with DC gas metal arc welding, pulsed gas metal arc welding, Fronius cold metal transfer (CMT), autogenous laser and laser hybrid welding on butt welds in 4 mm thick DH36 ship plate. Laser and laser hybrid welding were found to produce the lowest distortion. Nevertheless, a considerable improvement can be achieved with the pulsed gas metal arc welding and CMT processes. The paper seeks to understand the relationship between heat input, fusion area, measured distortion and the residual stress predicted from a simple numerical model, and the residual stresses validated with experimental data.

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The formation of large residual stresses continues to be a problematic side effect of all common welding processes. In this work, localised high pressure rolling of gas metal arc welds to relieve these residual stresses has been investigated using strain gauging and neutron diffraction. Rolling was found to remove undesirable tensile stresses and even induce large compressive ones, though only when applied after rather than during welding. Strain measurements taken during combined welding and rolling operations show that this is because material at the weld line continues to yield as it cools. This erases any beneficial effect on the stress distribution of rolling at high temperature. A method of rolling using an oscillating force is also presented and found to be just as effective as the equivalent static force process.

The changes of the three dimensional architecture of a eutectic AlSi12 alloy during heat treatment are revealed by means of synchrotron holotomography. The non‐destructive nature of the holotomography technique allows to analyze the same volumes in different thermal conditions. The results show a disintegration of the interconnected eutectic Si‐lamellae into isolated elongated particles. The load carrying capacity of both types of Si morphologies is studied by in situ neutron diffraction during compression tests. The experimental results are compared to those obtained using a micromechanical model developed for metal matrix composites based on a homogenization approach. The correlation between experiments and calculations shows that the interconnectivity of Si must be considered to account for the strength exhibited by the eutectic alloy. The present study bridges the gap between the already available two‐dimensional studies of architecture and properties of the binary AlSi12 alloy and new three‐dimensional studies of more complex systems based on this alloy.