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Most commercially available laser powder bed fusion (L-PBF) systems are limited to process one material at a time. The ability to spatially apply multiple materials within the same component will strongly expand the available design space for engineers. A typical problem with multi-material components is stress concentration at discrete material interfaces. Functionally graded interfaces could be used to overcome this limitation. In this work, an open-architecture L-PBF system from Aurora Labs was used to mix and process stainless steel 316L and maraging steel MS1 powder. Thereby, continuous and discrete interfaces between both materials were generated and characterized regarding microstructure, micro-hardness, and elemental composition. An L-PBF process window was found to gradually change the composition of 316L to MS1 creating a continuous interface. The controlled mixing of the powders in each layer indicates the versatility of the powder dispensation setup for multi-material combinations. This contribution will further pave the way towards the development of functionally graded L-PBF components. Metal additive manufacturing, multi-material, functionally graded components, adaptive process control, MS1, 316L
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... AM enables the building of topologically optimised and integrated composite parts according to digital 3D design data [2]. Particularly, metal-based powder bed fusion using a laser beam (PBF-LB/M), which is one such AM technique, is expected to be applied to mechanical parts, such as a customised part with a lattice structure [3], a highly functional mould with conformal cooling channels [4], and a functionally graded part [5]. However, this technique suffers from a lack of fusion and the formation of defects during layer building because of the stochastic arrangement of the deposited powder on the bed and the continuous fluctuation of laser-powder interaction, respectively [6]. ...
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The building of practical parts involves the application of metal-based powder bed fusion using a laser beam (PBF-LB/M), owing to its high-precision manufacturing. However, the quality of built parts obtained via the PBF-LB/M process varies with the building conditions, and a thorough understanding of the building mechanism has not been achieved owing to the complex and interrelated process parameters involved. The incident angle of the laser beam, which changes on the platform during the laser beam scan owing to the designed three-dimensional data, is among the principle parameters that affect the building aspects. In this study, the melt pool in the single-track formation during the PBF-LB/M process was visualised using a high-speed camera, and the influence of the laser incident angle on the ejection characteristics of spatter particles formed around the laser-irradiated area was investigated. Consequently, the spatter particles and metal vapour jets behaviour varied with the laser incident angle. There was a reduction in number of spatter particles owing to the origin of the incident direction being from behind the laser irradiation area. Additionally, the laser incident angle affected the melt pool morphology because of the depression in the melting. Furthermore, the burial depth of the pores varied with the laser incident angle, and was related to the depth of the depression during the melt pool formation.
... Tey et al. [15] fabricated a 316L/Ti6Al4V multi-material component by applying Cu alloy as the interlayer during LPBF, and the critical interface was found at Cu alloy/Ti6Al4V which affected the strength of the part. An open-architecture LPBF system was developed by Nadimpalli et al. [16] to gradually change the sample composition from 316L to MS1 by mixing powders with controlled measures. Han et al. [17] manufactured Titanium/hydroxyapatite (Ti/HA) gradient samples with a quasi-continuously transitional method during LPBF, and they found that the addition of HA improved the hardness of the part while reduced the fracture hardness. ...
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Laser powder bed fusion (LPBF) of multi-material and functionally graded materials (FGM) has attracted significant research interest due to its ability to fabricate components with superior performance compared with those manufactured with single powder material. However, the forming mechanisms of various defects remain unknown. In this paper, a DEM-CFD model was first established to obtain an in-depth understanding of this process. It was discovered that the defects including partially melted and un-melted Invar36 powder were embedded in the lower level of the powder layer; this was attributed to the low laser absorptivity, low melting point and high thermal conductivity of the Cu10Sn powder. Inter-layer defects were more likely to occur with an increased powder layer thickness. In addition, the scanned track width was found related to an equilibrium achieved among the thermal properties of the powder mixture. Process parameters were optimised to obtain FGM structures without defects in both horizontal and vertical directions. Invar36/Cu10Sn samples were fabricated with a multi-material LPBF system using different mixed powder contents and laser volumetric energy densities (VEDs). By increasing the VED, fewer defects were observed between the interface of two processed powder layers, which had a good agreement with the modelling results.
... Hence, there has not been much research on multi-metal printing using L-PBF. A brief overview of other multi-metal processing methods is given in Supplementary Materials Section 2. To date, fabrication of different multi-metal parts using L-PBF have been explored such as Inconel 625/steel [138], tantalumtungsten/steel [138], tool steel/copper-chromium-zirconium [139], tool steel H13/copper [140], aluminium alloy/copper alloy [14], 316L stainless steel/copper alloy [141], TiB 2 /Ti6Al4V [142], 316L stainless steel/MS1 maraging steel [143], Fe/Al12Si [144]. Besides L-PBF, electron beam powder bed fusion (EB-PBF) has also been used for fabricating Inconel 718/316L stainless steel [145] and Ti6Al4V/copper [146] multi-metal parts. ...
While significant progress has been made in understanding laser powder bed fusion (L-PBF) as well as the fabrication of various materials using this technology, there is still limited adoption in the industry. One of the key obstacles identified is the lack of materials that can truly manufacture functional parts directly with L-PBF. This paper covers the emerging research on in-situ alloying and multi-metal processing. A comprehensive overview of the underlying scientific topics behind them is presented. The current state of research and progress from different perspectives (the materials and L-PBF processing parameters) are reviewed in order to provide a basis for follow-up research and development of these approaches. Defects, especially those associated with these two material processing routes, are also elucidated by discussing the mechanisms of their formation, including the main influencing factors, and the tendency for them to occur. Future research trends and potential topics are illustrated. The final part of this paper summarizes findings from this review and outlines the possibility of in-situ alloying and multi-metal processing using L-PBF.
Additive manufacturing (AM) of metallic components is mainly based on directed energy deposition (DED) and powder bed fusion (PBF). However, most of the fabricated components are made of a single material. Over the last decade, with an attempt to integrate geometry, functionality, and distributed material properties, the investigation into multi‐material AM (MMAM) has emerged. In this chapter, MMAM technologies based on laser‐based DED (L‐DED), laser‐based PBF (L‐PBF), and wire arc additive manufacturing (WAAM) are introduced including fundamentals of design, working principles of MMAM technologies, manufacturing of functionally graded components (metal–metal, metal–ceramic, and metal–polymer), modeling and simulation, potential applications, and future challenges.
Additive manufacturing (AM) of metallic components is mainly based on directed energy deposition (DED) and powder bed fusion (PBF). However, most of the fabricated components are made of a single material. Over the last decade, with an attempt to integrate geometry, functionality, and distributed material properties, the investigation into multi‐material AM (MMAM) has emerged. In this chapter, MMAM technologies based on laser‐based DED (L‐DED), laser‐based PBF (L‐PBF), and wire arc additive manufacturing (WAAM) are introduced including fundamentals of design, working principles of MMAM technologies, manufacturing of functionally graded components (metal–metal, metal–ceramic, and metal–polymer), modeling and simulation, potential applications, and future challenges.
Additive manufacturing offers great potential and versatility for manufacturing high-quality and geometrically complex components. Multi-material laser-powder bed fusion is an emerging additive manufacturing approach where multiple materials are combined in order to manufacture multi-material components with new possibilities in product design and spatially tailored properties. Several multi-material delivery systems have been developed and a broad spectrum of applications have been demonstrated using multi-material laser-powder bed fusion. This work provides an overview in terms of architecture, construction and applications of all existing multi-material delivery systems developed for multi-material laser-powder bed fusion. Numerous challenges related to the deposition and processing of multi-materials which have been reported are discussed and potentials, which emerged through the use of multi-material laser-powder bed fusion are discussed together with the future perspectives.
Dies for high pressure die casting (HPDC) has traditionally been manufactured by machining from slabs of tool steel. Currently, the possibility of manufacturing them using additive manufacturing is being explored. This provides some advantages such as the possibility of making conformal cooling channels. However, the size of the dies is often larger than can be handled in most metal printers Still, it is possible to partly print the die by adding cores with intricate conformal cooling on a traditionally manufactured die base. In this paper, a feasibility study of using selective laser melting (SLM) to print cores of maraging steel directly onto a die base is explored. Results shows that the strength of the bond between the two metals is sufficient, and that the connection between the drilled and printed tooling channels can be made. The paper reasons on the expected impacts on the tooling industry showing potential for extended die life and recovery of die bases via re-manufacturing.
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The present work explores for the first time additive manufacturing of powder mixtures consisting of Chromium Nitride (Cr2N) and AISI 316L with laser powder bed fusion (L-PBF). The addition of 2.5 wt% Cr2N to an AISI 316L powder resulted in the successful dissolution of both chromium and nitrogen into a fully austenitic stainless steel microstructure. The nitrogen content was augmented from 0.09 wt% in the as-delivered AISI 316L powder to 0.31 wt% in the L-PBF built part, causing a slight expansion of the austenite lattice. Elongated austenite grains with an internal cellular substructure were obtained in both the Cr2N modified 316L and the 316L specimens manufactured by L-PBF. The addition of nitrogen (and chromium) from Cr2N resulted in a Vickers hardness increase of about 40 HV0.1, mainly by interstitial solid solution strengthening. The modification of 316L by the addition of Cr2N significantly improved the corrosion resistance. The improved hardness and corrosion resistance while retaining the manufacturability and cellular microstructure illustrate the potential for modifying the composition and properties of L-PBF 316L with targeted dosing with Cr2N powders.
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In this review paper, the authors investigate the state of technology for hybrid- and multi-material (MM) manufacturing of metals utilizing additive manufacturing, in particular powder bed fusion processes. The study consists of three parts, covering the material combinations, the MM deposition devices, and the implications in the process chain. The material analysis is clustered into 2D- and 3D-MM approaches. Based on the reviewed literature, the most utilized material combination is steel-copper, followed by fusing dissimilar steels. Second, the MM deposition devices are categorized into holohedral, nozzle-based as well as masked deposition concepts, and compared in terms of powder deposition rate, resolution, and manufacturing readiness level (MRL). As a third aspect, the implications in the process chain are investigated. Therefore, the design of MM parts and the data preparation for the production process are analyzed. Moreover, aspects for the reuse of powder and finalization of MM parts are discussed. Considering the design of MM parts, there are theoretical approaches, but specific parameter studies or use cases are not present in the literature. Principles for powder separation are identified for exemplary material combinations, but results for further finalization steps of MM parts have not been found. In conclusion, 3D-MM manufacturing has a MRL of 4–5, which indicates that the technology can be produced in a laboratory environment. According to this maturity, several aspects for serial MM parts need to be developed, but the potential of the technology has been demonstrated. Thus, the next important step is to identify lead applications, which benefit from MM manufacturing and hence foster the industrialization of these processes.
Functionally grading material composition in laser powder bed fusion (LPBF) provides the potential for complex components with spatially tailored properties. Novel LPBF machine technology is described addressing a combination of the significant challenges for multiple material fabrication including grading in both the vertical and horizontal directions, clearing of unwanted powder compositions from previous layers, local processing parameter changes, grading of materials with disparate melting temperature and demonstration of complex geometries with graded composition. Multi-directional graded composition components are presented for titanium to tantalum and nickel-based superalloy 718 to copper-alloy GRCop-42, demonstrating the potential for tailored, location specific functionality.
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