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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Abstract. Wire + Arc Additively Manufactured components contain significant residual stresses that manifest in distortion. Each layer of an additively manufactured wall was rolled with the aim of reducing the residual stress. Neutron diffraction and contour method measurements show that the residual stresses were reduced -particularly at the boundary with the substrate. The process also reduced distortion, and refined the microstructure which may facilitate implementation on aerospace components. IntroductionAdditive manufacture describes a collection of manufacturing processes where components are manufactured by breaking a CAD model down into layers each of which are then deposited using a variety of techniques that are either powder or wire-based. One of those techniques, Wire + Arc Additive Manufacture (WAAM) [1] uses deposition processes based on welding to deposit metal in the form of wire. The process could have a significant and disruptive impact on manufacturing due to: reduced consumption of raw materials; reduced manufacturing costs and lead times; and increased design flexibility.WAAM is characterised by a number of issues that are slowing its wider implementation. The long, columnar grains in the microstructure of AM components leads to anisotropy [2]. Moreover, Ding et al. [3] describes how steel components are affected by residual stresses and distortion during WAAM. The distortion leads to poor build tolerances, while the residual stress negatively affects part performance. Recently, large residual stresses have been measured in titanium WAAM components by Hoye et al. [4]. Residual stresses have also been reported in parts manufactured by electron beam [5] and laser-based [6,7] additive manufacture processes.In the related field of welding, one way of counteracting the effect of differential thermal contraction is to induce a compensating plastic strain in the deposited region by mechanical means. Coules et al. [8] describes how high-pressure rolling can also induce the plastic strain required for relaxation of residual stress in welded joints. When carried out after welding, this method comprehensively changed the residual stress distribution, and produced large compressive stresses in the weld. A key advantage of rolling is that it can cause plastic deformation over the entire weld cross-section, rather than just at the surface which is often the case with peening techniques. This counteracts the residual stress caused by welding more effectively, and reduces distortion of the welded component as demonstrated by Wen et al. [9].In previous work [10] rolling was applied between passes (after cooling to room temperature) of WAAM deposited walls. Two different roller profiles were investigated: the first, called the "profiled" roller, used a grooved profile that matched the top surface of the WAAM deposit. The second, called the "slotted" roller used an additional 10 mm deep slot to constrain the lateral deformation of the deposited material. Distortion was significantly reduced and in the case of ...

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Despite its excellent elemental properties, lightweight nature and good alloying potential, scandium has received relatively little attention in the manufacturing community. The abundance of scandium in the Earth's crust is quite high. It is more abundant than silver, cobalt, lead and tin. But, because scandium is so well dispersed in the lithosphere, it is notoriously difficult to extract in commercial quantities-hence low market availability and high cost. Scandium metallurgy is still a largely unexplored field-but progress is being made. This review aims to summarise advances in scandium metallurgical research over the last decade. The use of scandium as a conventional minor addition to alloys, largely in structural applications, is described. Also, more futuristic functional applications are discussed where details of crystal structures and peculiar symmetries are often of major importance. This review also includes data obtained from more obscure sources (especially Russian publications) which are much less accessible to the wider community. It is clear that more fundamental research is required to elevate the status of scandium from a laboratorybased curiosity to a mainstream alloying element. This is largely uncharted territory. There is much to be discovered.

The effect of helium-neon laser irradiation (632.5 nm) on A delta- and C-fiber sensory afferents was investigated in the rabbit cornea, to determine the physiologic basis for reports that low power (0.1-5 mW) helium-neon (He-Ne) lasers produce acute analgesia and alleviate chronic pain. Multiple and single unit extracellular recordings from nociceptive corneal afferent nerves (C-fiber cold, C-fiber chemical, A delta mechanical and A delta bimodal) were used to study the effects of He-Ne laser radiation upon the electrophysiologic responses to mechanical, thermal, chemical and electrical stimulation of the cornea. Action potentials were analyzed for latency, amplitude, rise time, duration and frequency. Exposure of the neural receptive field and/or nerve bundle to a 4-mm diameter He-Ne laser (0-5 mW; 0-1800 sec) did not alter spontaneous or evoked neural activity. In addition, single unit action potential parameters were not altered by laser irradiation. Modeling of thermal changes produced by He-Ne radiation on corneal nerves indicated that effects predicted for receptor and axonal depths in both skin and cornea were minimal (less than 0.15 degrees C) and unlikely to alter sensory transduction or transmission.