Additive manufacturing has provided a pathway for inexpensive and flexible manufacturing of specialized components and one-off parts. At the nanoscale, such techniques are less ubiquitous. Manufacturing at the nanoscale is dominated by lithography tools that are too expensive for small- and medium-sized enterprises (SMEs) to invest in. Additive nanomanufacturing (ANM) empowers smaller facilities to design, create, and manufacture on their own while providing a wider material selection and flexible design. This is especially important as nanomanufacturing thus far is largely constrained to 2-dimensional patterning techniques and being able to manufacture in 3-dimensions could open up new concepts. In this review, we outline the state-of-the-art within ANM technologies such as electrohydrodynamic jet printing, dip-pen lithography, direct laser writing, and several single particle placement methods such as optical tweezers and electrokinetic nanomanipulation. The ANM technologies are compared in terms of deposition speed, resolution, and material selection and finally the future prospects of ANM are discussed. This review is up-to-date until April 2014.

Three-dimensional transmission electron microscopy (3D-TEM) is a powerful technology that provides 3D characterization of the internal details of a material. In this work, for the first time, 3D-TEM was used to characterize a laser-sintered polymer nanocomposite. The dispersion of carbon nanotubes (CNTs) in the laser-sintered polyamide 12 (PA12)-CNT nanocomposite parts was evaluated. At first, to prepare 3D-TEM samples at specific locations, a focused ion beam technique was used. Then, high quality two-dimensional (2D)-TEM images were achieved at various scanning angles for the PA12-CNT laser-sintered sample. After that, 3D-TEM images were reconstructed by combining all the 2D-TEM images. Results revealed that the CNTs were agglomerate-free in the PA12-CNT parts after laser sintering, which helps to explain previously reported improvement in mechanical properties of laser-sintered PA12-CNT parts.

The fundamental factors of polymer powders, their importance for successful selective laser sintering (SLS) processing, and the outstanding position of polyamide 12 (PA12) powders in this connection are presented. Considering key factors, the combination of intrinsic and extrinsic properties necessary to generate a powder likely for SLS application is emphasized. Only a specific combination of indicated points leads to success. This is one reason for fewer materials commercially available to date for SLS application. PA12 and some dry blends based on PA12 are today the materials that are used to generate almost all commercial SLS parts. The specific performance of particular PA12 for SLS processing is unmatched from other polymers so far. Reasons are the precise molecular control of SLS polymers for thermal behavior (enlargement of sintering window) and the open chain structure. This is for generation of sufficient mechanical properties and to induce interlayer bonding of successively sintered layers to reduce anisotropic parts.

The media advertizes that soon everybody can manufacture models and parts of all kinds via computer-aided design –computer-aided manufacturing by additive manufacturing (AM) technologies. That can boost the do-it-yourself activities enormously. But it can also revolutionize the industries: Most conventional technologies of manufacture are profitable only in big lots of production. For single specimens and small lots of production, they are too expensive. But with AM, one or a few original or spare parts can be produced at low cost. However, to succeed in the market, the AM products must become competitive. They must have reproducibility of an exact shape, even in tiny details, a perfect surface and, above all, sufficient mechanical strength. This article deals with three-dimensional ink-jet printing with monomer inks and polymer powders. Since powder beds are always porous, the main aim was to fill the pores permanently with high amounts of the ink polymer. A new polymer powder that rapidly dissolves in monomer inks is reported.

It is known that polymers used in laser sintering (LS) change their intrinsic properties due to processing conditions that are close to the crystalline melting temperature. This paper evaluates the aging behavior of a thermoplastic polyurethane powder, comparing with to a commercially available LS elastomeric material (Duraform®Flex, 3D Systems). To represent a realistic production environment, the materials were aged during 14 processing cycles in the LS process without refreshing with virgin material. Following each aging cycle, both the powder and the sintered parts were examined for chemical and physical aging effects. The results showed that the materials observed could be used without refreshing throughout the 14 aging stages, however, changes in the processing behavior as well as in the parts' mechanical properties were evident. These changes were due to the differing aging states of the LS-powder showing an increase in the particle size affecting the bulk materials packing density. Modifications in the rheological properties can be seen in a decrease of molecular weight likely to reduce the mechanical strength of tensile specimens.

Laser sintering allows producing end-use parts directly from computer files with no tooling required. For these parts to be used in industrial applications, their mechanical properties throughout in-service applications must be examined. The aim of this article is to provide an understanding of the dynamic performance of laser-sintered Nylon 12 parts. To investigate the viscoelastic properties of the material, dynamic thermal mechanical analysis has been performed in different frequencies and temperatures. Tension–tension cyclic behavior of samples has been studied and creep is shown to have a great impact in such behavior in addition to fatigue. Stress relaxation plots are provided and compared with the cyclic loading plots validating the fact that samples experience a combination of creep and fatigue in tension–tension loading. Hysteresis loops indicate brittle crack propagation in the samples experiencing fatigue.

Material extrusion 3D printing (ME3DP) based on fused deposition modeling (FDM) technology is currently the most commonly used additive manufacturing method. However, ME3DP suffers from a limitation of compatible materials and typically relies upon amorphous thermoplastics, such as acrylonitrile butadiene styrene (ABS). The work presented here demonstrates the development and implementation of binary and ternary polymeric blends for ME3DP. Multiple blends of acrylonitrile butadiene styrene (ABS), styrene ethylene butadiene styrene (SEBS), and ultrahigh molecular weight polyethylene (UHMWPE) were created through a twin screw compounding process to produce novel polymer blends compatible with ME3DP platforms. Mechanical testing and fractography were used to characterize the different physical properties of these new blends. Though the new blends possessed different physical properties, compatibility with ME3DP platforms was maintained. Also, a decrease in surface roughness of a standard test piece was observed for some blends as compared with ABS.

In nature, biological structures often exhibit complex geometries that serve a wide range of specific mechanical functions. One such example are the ammonites, a large group of extinct mollusks, which produced elaborate, fractal-like hierarchical suture interface patterns. This report experimentally explores the influence of hierarchical suture interface designs on mechanical behavior by taking advantage of additive manufacturing and its ability to fabricate complex geometries. In addition, structure/property relationships of additively manufactured multi-material prototypes are investigated. It is shown that increasing the order of hierarchy amplifies stiffness by more than an order of magnitude. Tensile strength can also be tailored by changing the order of hierarchy, which alters the normal to shear stress ratio of the interfacial layer. The addition of failure mechanisms with increased order of hierarchy also significantly increases the toughness. Therefore, hierarchical suture interfaces can be used to diversify the mechanical behavior of additively manufactured materials.

Mechanical properties of parts constructed with additive manufacturing (AM) technologies are highly influenced by raw material and process characteristics. It is widely assumed that a certain degree of anisotropy should be expected in AM parts due to their layer-upon-layer nature. Present work focuses on the PolyJet process, where each layer is built by selective jetting of photopolymers upon flat surfaces and subsequent UV radiation curing. An extensive experimental program was carried out to find out if the so-constructed parts present viscoelastic behavior and if their mechanical characteristics also depend on part orientation. Both hypotheses have been proven true, so a viscoelastic orthotropic-like behavior shall be expected in PolyJet manufactured part. Nevertheless, a significant improvement on material properties has been found for nearly vertical building orientations. This unexpected behavior is related to a shielding effect upon UV curing caused by support material.

Materials and processes used for medical applications should have specific attributes. For bone repair and reconstruction, controlled open porosity and osteoconductivity are essential apart from mechanical strength and biocompatibility. Several forms of calcium phosphates are often used for these applications, considering properties similar to bone minerals, but often in combinations with other biopolymers. Polymethyl methacrylate (PMMA) and β-tricalcium phosphate (β-TCP) are identified as a suitable combination for the current research, considering specific properties both individually and in combinations, when processed by different means for specific medical applications. Specific responses of the biocomposite material formed by mechanically mixing the two materials in the powder form to selective laser sintering (SLS) under varying conditions are investigated. The results indicate the suitability of the material system for SLS, while controlled porosity and mechanical property combinations are possible by optimizing material composition and process parameters.

Additive manufacturing (AM) holds tremendous promise in terms of revolutionizing manufacturing. However, fundamental hurdles limit the widespread adoption of this technology. First, production rates are extremely low. Second, the physical size of the parts is generally small, less than a cubic foot. Third, the mechanical properties of the polymer parts are generally poor, limiting the potential for direct part replacement and functional use of the polymer components. This article describes various ways in which carbon fibers (CFs) can be used to address these fundamental hurdles. First, CF-reinforced polymers developed for AM have demonstrated specific strengths approaching aerospace-quality aluminum. Second, CF additions can radically reduce the distortion and warping of the material during deposition, which enables large-scale, out-of-the-oven, high deposition rate manufacturing. Finally, the complementary nature of CF technology and AM is discussed, showing how merging the two manufacturing processes enables the construction of complex components that would not be possible with either technology alone.

The current work provides an overview of the state-of-the-art in polymer and metal additive manufacturing and provides a progress report on the science and technology behind gradient metal alloys produced through laser deposition. The research discusses a road map for creating gradient metals using additive manufacturing, demonstrates basic science results obtainable through the methodology, shows examples of prototype gradient hardware, and suggests that Compositionally Graded Metals is an emerging field of metallurgy research.

The selective-laser-melting (SLM) technique is an outstanding new production technology that allows for time-efficient fabrication of highly complex components from various metals. SLM processing leads to the evolution of numerous microstructural features strongly affecting the mechanical properties. For enabling application in envisaged fields the development of a robust production process for components subjected to different loadings is crucially needed. With regard to the behavior of SLM components subjected to cyclic loadings, the damage evolution can be significantly different depending on the raw material that is used, which is, in this case, highly ductile austenitic stainless steel 316L and high-strength titanium alloy TiAl6V4. By means of a thorough set of experiments, including postprocessing, mechanical testing focusing on high-cycle fatigue and microstructure analyses, it could be shown that the behavior of TiAl6V4 under cyclic loading is dominated by the process-induced pores. The fatigue behavior of 316L, in contrast, is strongly affected by its monotonic strength.

Additive manufacturing technologies, also known as 3D printing, have demonstrated the potential to fabricate complex geometrical components, but the resulting microstructures and mechanical properties of these materials are not well understood due to unique and complex thermal cycles observed during processing. The electron beam melting (EBM) process is unique because the powder bed temperature can be elevated and maintained at temperatures over 1000 °C for the duration of the process. This results in three specific stages of microstructural phase evolution: (a) rapid cool down from the melting temperature to the process temperature, (b) extended hold at the process temperature, and (c) slow cool down to the room temperature. In this work, the mechanisms for reported microstructural differences in EBM are rationalized for Inconel 718 based on measured thermal cycles, preliminary thermal modeling, and computational thermodynamics models. The relationship between processing parameters, solidification microstructure, interdendritic segregation, and phase precipitation (δ, γ′, and γ″) are discussed.

Additive manufacturing (AM) opens new possibilities for functionalization and miniaturization of components in many application fields. Different technologies are known to produce single- or multimaterial components from polymer ceramic or metal. Our new approach – thermoplastic 3D printing – makes it possible to produce metal–ceramic composites. High-filled metal and ceramic suspensions based on thermoplastic binder systems were used as they solidify by cooling. Hence, the portfolio of applicable materials is not limited. Paraffin-based thermoplastic feedstocks with stainless steel powder (17-4PH) and zirconia powder (TZ-3Y-E) were developed with an adapted powder content of 47 vol% steel and 45 vol% zirconia. As compared to other AM technologies, the suspensions were only applied at particular points and areas and not on the whole layer. The printed samples were conventionally debinded and sintered. FESEM studies of the cross-section of the sintered samples showed a homogenous, dense microstructure and a very good connection between the different materials and layers.

This study presents results of selective laser melting (SLM), powder metallurgy (PM), and casting technologies applied for producing Ti–TiB composites from Ti–TiB2 powder. Diffraction patterns and microstructural investigations reveal that chemical reaction occurred between Ti and TiB2 during all the three processes, leading to the formation of Ti–TiB composites. The ultimate compressive strength of SLM-processed and cast samples are 1421 and 1434 MPa, respectively, whereas the ultimate compressive strengths of PM-processed 25%, 29%, and 36% porous samples are 510, 414, and 310 MPa, respectively. The Young's moduli of porous composite samples are 70, 45, and 23 GPa for 25%, 29%, and 36% porosity levels, respectively, and are lower than those of SLM-processed (145 GPa) and cast (142 GPa) samples. Fracture analysis of the SLM-processed and cast samples shows shear fracture and microcracks across the samples, whereas failure of porous samples occurs due to porosities and weak bonds among particles.

The effect of the beam scanning speed on part microstructures in the powder-bed electron beam additive manufacturing (EBAM) process was investigated in this research. Four levels of the beam speed were tested in building EBAM Ti–6Al–4V samples. The samples were subsequently used to prepare metallographic specimens for observations by optical microscopy and scanning electron microscopy. During the experiment, a near-infrared thermal imager was also used to acquire build surface temperatures for melt tool size estimates. It was found that the X-plane (side surface) shows columnar prior β grains, with the width in the range of about 40–110 µm, and martensitic structures. The width of columnar grains decreases with the increase of the scanning speed. In addition, the Z-plane (scanning surface) shows equiaxed grains, in the range of 50–85 µm. The grain size from the lowest beam speed (214 mm/s) is much larger compared to other samples of higher beam speeds (e.g., 376–689 mm/s). In addition, increasing the beam scanning speed will also result in finer α-lath. However, the porosity defect on the build surface also becomes severe at the highest scanning speed (689 mm/s).

Selective laser melting (SLM) process was used to prepare the nanocrystalline titanium carbide (TiC)-reinforced Inconel 718 matrix bulk-form nanocomposites in the present study. An in-depth relationship between SLM process, microstructures, properties, and metallurgical mechanisms was established. The insufficient laser energy density (η) input limited the densification response of shaped parts due to the formation of either larger-sized pore chains or interlayer micropores. The densification of SLM-processed part increased to a near-full level as the applied η was properly settled. The TiC reinforcements generally experienced successive changes from severely agglomerated in a polygon shape to the uniformly distributed with smoothened and refined structures on increasing the applied η, while the columnar dendrite matrix exhibited strong epitaxial growth characteristic concurrently. The optimally prepared fully dense part achieved a high microhardness with a mean value of 419 HV0.2, a considerably low friction coefficient of 0.29, and attendant reduced wear rate of 2.69 × 10−4 mm3/N m in dry sliding wear tests. The improved densification response, SLM-inherent nonequilibrium metallurgical mechanisms with resultant uniformly dispersed reinforcement microstructures, and elevated microhardness were believed to be responsible for the enhancement of wear performance.

Ultrasonic consolidation is a rapid manufacturing process for metal matrix composite (MMC) preimpregnated composite (prepreg) tapes or foils. One of the main advantages of this manufacturing technique over traditional MMC methods is the ability to produce multimaterial structures through the layer-by-layer build-up procedure. The interface of an ultrasonically consolidated bimaterial interface has not been studied on the nanometer scale through transmission electron microscopy (TEM), which can help better understand the bonding mechanisms. An ultrasonically consolidated copper–aluminum (Cu–Al) interface was explored through TEM, through which a 1-µm recrystallized subgrain region was observed on the aluminum side and dislocation pile-up was viewed between the subgrain and bulk aluminum interface. Phase changes were suspected due to varying contrast bands parallel to the Cu–Al interface and were confirmed through an x-ray energy dispersive spectroscopy (XEDS) linescan. An apparent diffusion coefficient was calculated, which supported bulk diffusion at the measured welding temperature of 493 °C and subgrain size of 20–50 nm.