Additive manufacturing of metallic components – Process, structure and properties

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Additive manufacturing of metals

Selective Laser Melting (SLM) is a particular rapid prototyping, 3D printing, or Additive Manufacturing (AM) technique designed to use high power-density laser to melt and fuse metallic powders. A component is built by selectively melting and fusing powders within and between layers. The SLM technique is also commonly known as direct selective laser sintering, LaserCusing, and direct metal laser sintering, and this technique has been proven to produce near net-shape parts up to 99.9% relative density. This enables the process to build near full density functional parts and has viable economic benefits. Recent developments of fibre optics and high-power laser have also enabled SLM to process different metallic materials, such as copper, aluminium, and tungsten. Similarly, this has also opened up research opportunities in SLM of ceramic and composite materials. The review presents the SLM process and some of the common physical phenomena associated with this AM technology. It then focuses on the following a...

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Review of selective laser melting : materials and applications

https://research.birmingham.ac.uk/portal/files/19592544/NR_mod_CL31_12_9_14_F4.pdf

Selective laser melting of AlSi10Mg alloy: Process optimisation and mechanical properties development

The current market is in a phase of accelerated process of change, that leads companies to innovate in new techniques or technologies to respond as quickly as possible to the everchanging aspects of the global environment. The economy of a country is heavily dependent on new and innovative products with very short development time. Companies, currently, have considerable success, only if they develop the ability to respond quickly to changing of customer needs and to use new innovative technologies. In this context, the companies that can offer a greater variety of new products with higher performance resulting in advantage over the other. At the heart of this environment there is a new generation of customers, who forced organizations to research new technologies and techniques to improve business processes and accelerate product development cycle. As a direct result, factories are forced to apply a new philosophy of engineering as the Rapid Response to Manufacturing (RRM). The concept of the RRM uses products previously designed to support the development of new products. The RRM environment was developed by integrating the various technologies, such as CAD-based modelling, the knowledge-based engineering for integrated product and process management and the direct production concepts. Direct production uses prototyping, tooling and rapid manufacturing technologies to quickly test the design and build the part (Cherng et al., 1998). Among RRM technologies, Rapid (RP) and Virtual (VP) Prototyping are revolutionizing the way in which artefacts are designed. Rapid Prototyping (RP) technologies embraces a wide range of processes for producing parts directly from CAD models, with little need for human intervention; so, designers can produce real prototypes, even very complex, in a simple and efficient way, allowing them to check the assembly and functionality of the design, minimizing errors, product development costs and lead times (Waterman & Dickens, 1994). The SLS technology was developed, like other RP technologies, to provide a prototyping technique to decrease the time and cost of the product cycle design. It consists of building a three dimensional object layer by layer selectively sintering or partial melting a powder bed by laser radiation.

/pdf/capabilities-and-performances-of-the-selective-laser-melting-4649jp2el5.pdf

Capabilities and Performances of the Selective Laser Melting Process

Selective laser melting (SLM) is a successful tool-free powder additive technology. The success of this manufacturing process results from the possibility to create complex shape parts, with intrinsic engineered features and good mechanical properties. Joining SLM steel to similar or dissimilar steel can overcome some limitations of the product design like small dimension, undercut profile, and residual stress concentration. In this way, the range of applications of the SLM process can be broadened. In this paper, the hybrid laser welding of selective laser molten stainless steel was investigated. A high-power fiber laser was coupled to an electric arc and austenitic stainless steel wrought and SLM parts were welded together. The power and speed parameters were investigated. The joints were analyzed in terms of weld bead profile, microstructure, microhardness, and tensile test. The efficiency of the welding process was evaluated through the line energy input versus the weld molten area.

Laser-arc hybrid welding of wrought to selective laser molten stainless steel

Ytterbium fiber laser welding of Ti6Al4V alloy

Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

Laser milling is a new, very flexible process for micro-fabrication, suitable for machining difficult-to-machine materials, like ceramics, dielectrics, carbide and hardened steel with good productivity and surface. Optimal selection of process parameters is highly critical for successful material removal and achieving high surface quality. It is crucial for Laser Milling to enhance the productivity of the process in terms of maximization of the material removal rate (MRR), calculated as the ratio between the volume of removed material and the process time, saving at the same time a good surface quality, and to correlate this index to the ablation depth and to surface roughness. In contrast, laser ablation suffers from the usual incompatibility of high ablation depths and good surface quality. The objective of this paper was to demonstrate that the careful laser choice and process optimization can result in a satisfactory compromise for both. This goal was achieved with a simultaneous statistical analysis of ablation depth, material removal rate and surface roughness. Moreover, a multi-objective statistical optimization was performed for improving machining productivity and surface quality. The dependence of the ablation depth, MRR and surface roughness on the laser fluence was also analyzed. All experimental tests were conducted on the 5754 aluminum alloy using a nanosecond Nd:YAG laser with a wavelength of 1064 nm.

Sabina Luisa Campanelli

Papers

Capabilities and Performances of the Selective Laser Melting Process

Laser-arc hybrid welding of wrought to selective laser molten stainless steel

Ytterbium fiber laser welding of Ti6Al4V alloy

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

Multi-objective optimization of laser milling of 5754 aluminum alloy