Metal additive manufacturing in the commercial aviation industry: A review

Gisario, Annamaria; Kazarian, Michele; Martina, Filomeno; Mehrpouya, Mehrshad

doi:10.1016/j.jmsy.2019.08.005

Cited by 406 publications

(160 citation statements)

References 205 publications

(263 reference statements)

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“…Laser Powder Bed Fusion (LPBF), in particular, consists in selective fusion of regions of a powder bed by means of a fast-scanning high-power laser beam. It is notably characterized by very high solidification and cooling rates, as high as 10 5 –10 6 °C/s, as well as repeated and sharp heating-and-cooling cycles as the laser beam travels over the powder bed and the consolidated parts according to the selected scanning strategy [ 1 , 2 , 3 , 4 , 5 , 6 ]. These unique characteristics, as opposed to conventional manufacturing, are responsible for the peculiar microstructure of LPBFed parts.…”

Section: Introductionmentioning

confidence: 99%

Electron Backscattered Diffraction to Estimate Residual Stress Levels of a Superalloy Produced by Laser Powder Bed Fusion and Subsequent Heat Treatments

et al. 2020

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Metal Additive Manufacturing and Laser Powder Bed Fusion (LPBF), in particular, have come forth in recent years as an outstanding innovative manufacturing approach. The LPBF process is notably characterized by very high solidification and cooling rates, as well as repeated abrupt heating and cooling cycles, which generate the build-up of anisotropic microstructure and residual stresses. Post-processing stress-relieving heat treatments at elevated temperatures are often required in order to release some of these stresses. The effects of 1 h–hold heat treatments at different specific temperatures (solutionizing, annealing, stress-relieve and low-temperature stress-relieve) on residual stress levels together with microstructure characterization were therefore investigated for the popular Alloy 625 produced by LPBF. The build-up of residual stress is accommodated by the formation of dislocations that produce local crystallographic misorientation within grains. Electron backscattered diffraction (EBSD) was used to investigate local misorientation by means of orientation imaging, thereby assessing misorientation or strain levels, in turn representing residual stress levels within the material. The heavily constrained as-built material was found to experience full recrystallization of equiaxed grains after solutionizing at 1150 °C, accompanied by significant drop of residual stress levels due to this grains reconfiguration. Heat treatments at lower temperatures however, even as high as the annealing temperature of 980 °C, were found to be insufficient to promote recrystallization though effective to some extent to release residual stress through apparently dislocations recovery. Average misorientation data obtained by EBSD were found valuable to evaluate qualitatively residual stress levels. The effects of the different heat treatments are discussed and suggest that the peculiar microstructure of alloys produced by LPBF can possibly be transformed to suit specific applications.

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Section: Introductionmentioning

confidence: 99%

Electron Backscattered Diffraction to Estimate Residual Stress Levels of a Superalloy Produced by Laser Powder Bed Fusion and Subsequent Heat Treatments

et al. 2020

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“…In its early age, additive manufacturing was mainly employed for prototyping, with scientists and designers taking advantage of its efficient and costeffective technology in building models to be used for theoretical studies or product development. Nowadays, the potential of additive manufacturing is exploited in several fields [3], including the aerospace [4], automotive [5], construction [6] and healthcare sectors [7,8]. New frontiers are being explored in the field of advanced materials science [9,10], with applications to the design of structured materials [11][12][13][14], stimuli-responsive materials [15][16][17] and bioprinting [18,19].…”

Section: Introductionmentioning

confidence: 99%

Laser-based additively manufactured polymers: a review on processes and mechanical models

et al. 2020

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Additive manufacturing (AM) is a broad definition of various techniques to produce layer-by-layer objects made of different materials. In this paper, a comprehensive review of laser-based technologies for polymers, including powder bed fusion processes [e.g. selective laser sintering (SLS)] and vat photopolymerisation [e.g. stereolithography (SLA)], is presented, where both the techniques employ a laser source to either melt or cure a raw polymeric material. The aim of the review is twofold: (1) to present the principal theoretical models adopted in the literature to simulate the complex physical phenomena involved in the transformation of the raw material into AM objects and (2) to discuss the influence of process parameters on the physical final properties of the printed objects and in turn on their mechanical performance. The models being presented simulate: the thermal problem along with the thermally activated bonding through sintering of the polymeric powder in SLS; the binding induced by the curing mechanisms of light-induced polymerisation of the liquid material in SLA. Key physical variables in AM objects, such as porosity and degree of cure in SLS and SLA respectively, are discussed in relation to the manufacturing process parameters, as well as to the mechanical resistance and deformability of the objects themselves. Graphic abstract

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“…Nearly fully dense products can be fabricated with optimum combinations of process parameters [19]. Even the high standards of the aerospace industry can be met [20]. Nevertheless, it is still a challenge to produce a flawless product with the intended characteristics [21], and the building orientation has an impact on the mechanical properties [22].…”

Section: Introductionmentioning

confidence: 99%

Experimental Continuous Casting of Nitinol

Lojen

Stambolić

Batič

et al. 2020

Metals

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Commercially available nitinol is currently manufactured using classic casting methods that produce blocks, the processing of which is difficult and time consuming. By continuous casting, wherein molten metal solidifies directly into a semi-finished product, the casting and processing of ingots can be avoided, which saves time and expense. However, no reports on continuous casting of nitinol could be found in the literature. In this work, Φ 12 mm nitinol strands were continuously cast. Using a graphite crucible, smelting of pure Ni and Ti in a medium frequency induction furnace is difficult, because it is hard to prevent a stormy reaction between Ni and Ti and to reach a homogeneous melt without a prolonged long holding time. Using a clay-graphite crucible, the stormy reaction is easily controlled, while effective stirring assures a homogeneous melt within minutes. Strands of nearly equiatomic chemical compositions were obtained with acceptable surface quality. The microstructure of strands containing over 50 at. % Ni, consisted of Ti2Ni and cubic NiTi, whereas the microstructure of strands containing less than 50 at. % Ni consisted of TiNi3 and cubic NiTi. This is consonant with the results of some other authors, and indicates that the eutectoid decomposition NiTi → Ti2Ni + TiNi3 does not take place.

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Metal additive manufacturing in the commercial aviation industry: A review

Cited by 406 publications

References 205 publications

Electron Backscattered Diffraction to Estimate Residual Stress Levels of a Superalloy Produced by Laser Powder Bed Fusion and Subsequent Heat Treatments

Electron Backscattered Diffraction to Estimate Residual Stress Levels of a Superalloy Produced by Laser Powder Bed Fusion and Subsequent Heat Treatments

Laser-based additively manufactured polymers: a review on processes and mechanical models

Experimental Continuous Casting of Nitinol

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