Properties Of Additive Manufacturing Parts Research Articles

Investigating the effects of powder feeding rate on microstructure transformation in linear laser beam additive manufactured thick-walled structures

The coarse columnar crystals that grow through multiple layers are commonly observed in laser additive manufactured structures, with fractures tending to occur in regions where there are abrupt changes in grain morphology. This can lead to a degradation of the mechanical properties of the samples. In this study on laser additive manufacturing, thick-walled structures made of 304 stainless steel were created using a linear beam spot with a rectangular powder feeding nozzle. By adjusting the powder feeding rate to influence the thermal cycling characteristics during the laser additive manufacturing process, a hierarchical grain structure that combines coarse and fine equiaxed grains was achieved, enhancing the forming efficiency and overall mechanical performance of the structure. The results from the thermal cycling characteristics and microstructure analysis indicate that increasing the powder feeding rate during the additive manufacturing process can decrease the hierarchical cooling rate, temperature gradient, and heat accumulation effect. This reduction in turn decreases the grain size and facilitates the transformation of columnar crystals into equiaxed crystals. Furthermore, the transformation of low-angle grain boundaries into high-angle grain boundaries in the interlayer region helps to reduce stress concentration, weaken anisotropic tendencies, and mitigate intergranular fracture tendencies, ultimately improving the mechanical properties of the overall structure. In actual engineering applications, the powder flow can be adjusted to control the temperature gradient and cooling rate of the deposition layer, thereby altering the grain morphology and optimizing the mechanical properties of additive manufacturing parts.

Additive manufacturing of carbon nanocomposites for structural applications

Additive manufacturing (AM), also known as 3D printing, has attracted a lot of attention in science and technology in recent years. Improvement in AM processes and materials are necessary, particularly for structural and load-bearing components in mechanical applications. The addition of nano-fillers can potentially improve the mechanical properties of additively manufactured components, making them suitable for structural applications. Carbon nanofillers like graphene and carbon nanotubes are of special interest due to their exceptional properties. Several studies have already demonstrated the use of carbon nanofillers for improving the electrical properties of 3D printed components, facilitating their use in electrical and electronic applications. However, studies focusing on structural and mechanical applications have been limited, and are not widely known. This review seeks to fill this gap by exploring the effect of carbon nanofillers on the mechanical and thermal properties of AM parts and their use in structural applications. The effect of parameters like print orientation, nanofiller addition method, and nanofiller dispersion are also explored. The review points out that there are improvements in mechanical and thermal properties due to carbon nanofiller addition, which makes the AM components more suitable for structural application.

Coaxial Wire Laser-based Additive Manufacturing of AA7075 with TiC Nanoparticles

AA7075 is a heat treatable aluminium alloy widely used in aerospace and automotive applications due to its outstanding high strength-to-weight ratio. However, the implementation of this alloy in Additive Manufacturing (AM) processes has been limited due to its susceptibility to hot cracking. Moreover, selective evaporation of low boiling point elements Zn and Mg can cause gas porosity and diminish the mechanical properties of AM parts. Recent research revealed the effectiveness of nanoparticles additives to change the solidification behaviour of high-strength aluminium alloys and improve their weldability/printability. In this study, AA7075 enhanced with TiC nanoparticles was utilized as wire feedstock to create single and multi-layer samples with coaxial laser-directed energy deposition (L-DED). The response of the samples to precipitation hardening was studied, evaluating the microstructure and the microhardness before and after T6 heat treatment. Specimens were characterized using optical and electron microscopy and electron backscatter diffraction (EBSD). Crack-free and virtually porosity-free samples were fabricated, which exhibit a refined equiaxed grain structure with grain size <10μm. This confirms the ability of TiC nanoparticles to prevent columnar dendritic growth and promote heterogeneous nucleation. Microhardness values increased by 51 HV after T6 heat treatment and were uniform across the sample. Energy Dispersive Spectroscopy (EDS) analysis showed that there are evaporation losses of Zn and Mg. Considering the boiling temperatures of these elements, it is inferred that the molten pool reaches temperatures above 1090°C, and the partially melted zone temperature is between 907°C and 1090°C.

Revealing thermal behavior, cracking behavior, phase and microstructure formation of a ternary equiatomic alloy additively manufactured using directed energy deposition

Additive manufacturing (AM) of multi-principal element alloys (MPEAs) has recently attracted considerable attention. However, few studies focus on the thermal behavior, cracking behavior, and microstructure tunability of AM-processed MPEAs, which can significantly affect the final performance of AM MPEA parts. In this study, a ternary equiatomic MPEA CrCoNi, with a single-phase face-centered-cubic (FCC) structure, was fabricated by the AM process via directed energy deposition (DED) at different laser scan speeds (10, 30, and 50 mm/s), and special focus was given to the thermal behavior, cracking behavior and microstructure formation. The increase in the laser scan speed from 10 to 50 mm/s causes a sharp increase in temperature gradients and cooling rates by five-fold and seventeen-fold, reaching up to 1148 K/mm and 57,778 K/s, respectively, as in-situ measured by a high-speed and high-resolution thermal pyrometer. Furthermore, the increased laser scan speed induces the severe cracking, which propagates along high angle grain boundaries and is classified as solidification cracking based on the observed protruding dendrites from the cracked plane. Although the Scheil-Gulliver solidification predicts a very narrow critical temperature range of 16 K which is indicative of a low solidification cracking susceptibility, the high temperature gradient and the resulting high thermal stress, as evidenced from the high density of dislocations and stacking faults, are believed to trigger the severe solidification cracking of the CrCoNi MPEA deposited at a high laser scan speed of 50 mm/s. With increasing the laser scan speed, the grain structure changes from elongated grains, which are roughly oriented along the build direction, to a more heterogenous grain structure with elongated grains converging towards the centerline and equiaxed grains arranged between the columns of elongated grains. Furthermore, with increasing the laser scan speed, the cellular structures are refined down to ∼ 2 µm due to the increased cooling rates. These findings not only contribute to better understanding the thermal behavior, cracking behavior, and microstructure formation of the AM-processed MPEAs, but also pave a road for further enhancing the mechanical properties of AM parts via tuning the thermal behavior and microstructures.

Evaluation of residual stress reproducibility and orientation dependent fatigue crack growth in powder bed fusion stainless steel

The complex thermal gradients of additive manufacturing (AM) result in residual stress and distinctive grain morphologies that influence mechanical performance and contribute to concern regarding the fatigue properties of AM parts. In this study, residual stress, microstructure, and fatigue crack growth rate (FCGR) results were compared in AM Type 304L stainless steel produced by laser powder bed fusion (PBF) on different systems using similar process parameters. Residual stress measured in the build direction was remarkably consistent in all PBF builds. Backscatter electron large area images revealed similar grain morphologies in the different builds, all of which exhibited elongated grains in the build direction and inhomogeneous grain size and shape. Fatigue crack growth investigated both parallel and perpendicular to the build direction revealed higher measured crack growth rates in the near-threshold regime in both orientations of the PBF material compared to wrought material. The difference in near-threshold fatigue crack growth rates is attributed primarily to the influence of processing-induced residual stress quantified by the residual stress intensity factor. These values revealed consistent FCGR effects in each orientation across specimens extracted from different builds and were then used to reveal a convergence of the corrected FCGR data of all PBF and wrought specimens.

Hybrid manufacturing process combining laser powder-bed fusion and forging for fabricating Ti–5Al–5V–5Mo–3Cr–1Zr alloy with exceptional and isotropic mechanical properties

The metal additive manufacturing (AM) technology offers a unique advantage for production of complex and unconventional parts. However, the thermal history during the AM process often leads to anisotropy in the mechanical properties and inherent porosity of the deposits, which limits their performance compared to traditional forgings. To overcome these limitations, laser powder bed fusion (LPBF) technology was employed to produce single-step die-forging preforms. This innovative approach used coarse powder with a wide distribution of particle sizes to create a variety of molten pool structures, preventing the growth of columnar β grains in AM Ti–5Al–5V–5Mo–3Cr–1Zr (Ti-55531) alloys. The subsequent die-forging process eliminated inherent defects and regulated grains to be near-equiaxed, significantly improving the mechanical properties and reducing anisotropy. With proper post-heat treatment, the strength-ductility trade-off of the Ti-55531 alloy was adjusted to meet standards. This unconventional process route produced parts with isotropic and excellent mechanical properties, overcoming the defects and anisotropic properties of AM parts. This supplement to the traditional manufacturing process of high-performance titanium alloy parts holds great promise for future applications.

Introducing a new optimization parameter based on diffusion, coalescence and crystallization to maximize the tensile properties of additive manufacturing parts

Introducing a new optimization parameter based on diffusion, coalescence and crystallization to maximize the tensile properties of additive manufacturing parts

Effect of Line Width and Wall Count on the Compressive Strength of Single and Functionally Graded Additively Manufactured ABS Gyroid Structure

Additive Manufacturing (AM) has been in the manufacturing industry for more than a decade. It has aided in producing several intricate objects for several purposes. One of the most used techniques in AM is fused deposition modeling (FDM) wherein a plastic filament is heated to its melting point and deposited layer by layer in a build plate to form a 3D model. Acrylonitrile butadiene styrene (ABS) is one of the commonly used filaments because of its relatively good impact resistance and toughness, and workability in 3D printing various structures. The gyroid structure is a self-supporting structure that has a good strength-to-weight ratio. The compressive strength of single and multiple-layered structures of ABS gyroid lattice structure with different line widths, infill densities, and wall counts was observed. A 0.35 line width with an infill density of 25% and wall count of 3 has a compressive strength of 11.94 MPa, material consumption of 1.87 grams, and printing time of 14 min which makes it the most efficient design for single-layered structures. Among three-layered structures, the combination of infill densities of 25% and 35% is the most efficient with 0.45 line width and 3 walls. It has a compressive strength of 15.87 MPa, printing time of 13 min, and material consumption of 2.3 grams. Nowadays, there are limited research articles on AM of a single structure with gradual varying densities as well as the effect of lesser-known printing parameters on the mechanical properties of AM parts. This study aims to aid future research by providing data on single and functionally graded structures with different line widths and wall counts. With the information from this study, future researchers and designers can further optimize printing parameters to make an efficient design that is light and has sufficient mechanical strength to serve a specific function.

Effects of Different Scan Speeds on Microstructural and Corrosion Properties of Additively Manufactured HSLA Steels in 3.5% NaCl Solution

In automotive applications, high-strength low alloy (HSLA) steels are providing enhanced material properties, due to the high yield strength, less fragility, and lower weight, which also promotes lower fuel consumption. HSLA steels contain a small amount of carbon (under 0.2%) and also contain small amounts of alloying elements such as copper, nickel, niobium, vanadium, chromium, molybdenum and zirconium. This eliminates the toughness reducing effect of a pearlitic volume fraction, yet maintains and increases the material's strength by refining the grain size. Therefore, HSLA steels are used for structures intended to handle large amounts of stress or that need a good strength-to-weight ratio. Traditional manufacturing methods for steel (e.g., blast furnace or electric arc furnace methods) fail to provide the necessary optimization for best output in terms of performance and application. The quality of molten steel is greatly affected by scrap steel. The smelting period is longer, and the power consumption is large. In addition, these processes allow more impurities into the molten steel, which compromises the quality of the final product. However, additive manufacturing (AM) can can be used to fabricate HSLA steel components without these drawbacks. In addition, AM can provide a relatively faster process with low manufacturing costs, in comparison with traditional processing methods. Although AM has several benefits, studies shows that AM processes can result in HSLA steels with microstructural defects, such as non-homogeneity, internal cavities, inclusions, and impurities. Consequently, these microstructural features have a significant affect on the corrosion properties of AM parts as corrosion tends to initiate in defective regions. The AM processing parameters directly impact the microstructure of the fabricated part. Hence, it is important to understand the relationship between the AM processing parameters on resulting microstructural features. The present work evaluated the electrochemical corrosion properties of HSLA steels fabricated by AM via selective laser melting (SLM) under different processing conditions. The goal of the work was to investigate the role of microstructure on electrochemical corrosion in high-strength low alloy steels due to SLM processing conditions.Two types of HSLA steels, Fe 367 and Fe 398, were fabricated by AM via (SLM). Fe 398 differs from Fe 367 as it contains molybdenum and nickel. Each type was fabricated at a laser power of 100W, and scan speed of 600, 800, 100 and 1200 mm/s. The samples were exposed to 3.5% NaCl for 15 days, individually. To acquire the electrochemical corrosion data and to perform analysis, a Gamry reference 600 potentiostat/galvanostat was used. The electrochemical data were obtained by collecting the impedance spectra, and measuring the polarization resistance every 5 days. On day 15, cyclic polarization data was collected for each sample. These measurements helped to identify the localized corrosion as well as provide detailed information about the corrosion properties, such as passive layer growth, initiation and secession of pitting, and corrosion rate. The topography of the materials was observed by SEM before and after the corrosion tests. Energy Dispersive Spectroscopy (EDS) was performed on the samples to identify the chemical elements. The surface roughness was observed through confocal microscope.The Confocal and SEM images showed the change in surface microstructure and topographical properties of the samples before and after the corrosion testing. The difference in laser power and scan speed affected the microstructure and corrosion properties of the materials. As the samples were manufactured at same laser power, the scan speed was responsible for different topographical and corrosion behavior. Samples manufactured at lower scan speed showed less flaws on the surface of the materials than the samples manufactured at higher scan speed. Therefore, both Fe 398 and Fe 367 showed better surface topography at 600 mm/s and 800 mm/s. They also demonstrated significantly lower corrosion rate than the other samples. EDS identified chemical oxides and chlorides which were formed during the corrosion test. Overall, this work demonstrated that Fe 398 shows better microstructural and corrosion properties than Fe 367 at lower scan speed.

A modular framework to obtain representative microstructural cells of additively manufactured parts

The repeating nature of additive manufacturing (AM) translates into quasi-periodic repeating hierarchical microstructures, which vary depending on the working principle of the AM technology. The geometry and internal characteristics of these repeating microstructures affect the geometrical accuracy and mechanical properties of AM parts. We propose a modular and generic framework for AM microstructures to automatically determine a representative microstructural cell with average shape and microstructural information based on micrograph processing and morphological shape analyses. A general microstructural mapping procedure is presented to map and average different microstructural features inside the representative cell. Moreover, an extension of the method is proposed to recover a representative cell with a periodic shape as required for subsequent numerical micromechanical simulations under periodic boundary conditions to unravel process-structure–property relationships. The framework is demonstrated on a virtually generated microstructure and on the metallic and polymeric microstructure of two parts manufactured with different AM processes, showing the framework's versatility for different materials and AM technologies. The three test cases show the framework's modularity, where different procedures were applied to overcome the challenges of each particular case while keeping the primary method the same. We also discuss applications of the framework, such as enabling statistical investigations of spatial variations of the microstructural features across AM parts and providing essential input for microstructural and mechanical numerical simulations.

Additive manufacturing parts made of cobalt-chromium powders synthesized by electroerosion dispersion

Considering the standard procedure for producing globular powder particles, the authors of this paper propose to use the process of electroerosion dispersion for the production of globular particles of certain size for 3D technology. The proposed process is characterized with energy efficiency and sustainability. The waste cobalt-chromium alloy of the TsELLIT grade was used for the purposes of the study. Cobalt-chromium powders were produced by electroerosion dispersion on a special unit designed for conductive materials. Through experiments, it was established that as the particle dispersion rises, the baking process goes faster resulting in enhanced mechanical properties of the final products. Oxides present in fine-grained powders contribute to the intensity of the baking process as they are subject to reduction under heat impact. The spongy texture that forms when the oxides are gone from the metal surface appears to be more active compared with the oxide-film-free surface. The conducted study showed no changes to the structural and phase state of the specimens. Hence, all four specimens retained the following phases: Co, Cr, Ni и Cr3Ni2. The increasing dispersion and specific surface area of the powder leads to decreased porosity and increased microhardness in the final product. Due to the presence of particles of various sizes, the powder layer appears to be denser as cavities and micropores occurring between coarser particles get filled up. This results in lower roughness and higher compression and bend strength in baked parts. This study proves the possibility to control the structure and physico-mechanical properties of additive manufacturing parts made of powders that are obtained from waste cobalt-chromium alloys by electroerosion dispersion. This helps reduce the reliance on imported powders suitable for additive manufacturing while also cutting the cost of the final products.

Effect of Relative Density in In-Plane Mechanical Properties of Common 3D-Printed Polylactic Acid Lattice Structures.

Lattice structures are employed as lightweight sandwich cores, supports, or infill patterns of additive manufacturing (AM) components. As infill structures, the mechanical properties of AM parts are influenced by the infill pattern. In this work, we present the mechanical characterization of three commonly used infill patterns in AM, triangular, square, and hexagonal, and compare them with analytical and numerical models. Fused filament fabrication of polylactic acid (PLA) thermoplastic is used as the printing material for the compressive and tensile tests. First, a parametric analysis is performed by changing the infill density to obtain numerically and analytically the mechanical properties of the studied samples. Next, we compare the experimental results with numerical and analytical models and propose numerical correlations for high-density honeycombs. The stiffest infill pattern was the square, and the explanation is provided in detail. Also, there is a nonlinear correlation between density and the mechanical properties; however, the strongest part was not possible to determine with a significant statistical value. Finally, we propose simplified models for predicting the compressive and tensile response of AM PLA structures by considering the infill regions as homogenized structures.

Tribological characterization of Fused Deposition Modelling parts

The customisation or redesign of parts for Additive Manufacturing (AM) to meet the design requirements is an increasing trend. In this context, numerous studies related to the improvement of the mechanical properties of Additive Manufacturing parts used for static applications are emerging. However, the use of these parts in dynamic applications or in relative movement situations has not been deeply developed. Some studies have been focused on the fatigue properties of AM parts while few authors have analysed the sliding behaviour of these parts. This paper presents a characterisation of the wear behaviour of Fused Deposition Modelling (FDM) parts using Pin-on-Disc techniques with the aim of studying their possible implementation in dynamic applications.

A critical insight into lack-of-fusion pore structures in additively manufactured stainless steel

Despite the obvious advantages of additive manufacturing (AM) in producing metallic parts, defect formation remains a challenge that deleteriously impacts some critical materials properties of AM parts. Here, through electron microscopy and X-ray computed tomography (X-ray CT), new insights are revealed about lack-of-fusion (LOF) pores; the most common defect reported for AM. We show that LOF pores are not simply a void but a complex structure comprising oxide films decorating pore walls and grain refined regions with dislocation structures surrounding the pore. The formation of a thin nanocrystalline metallic layer on the pore wall is also observed. Spatter particles are the source of most LOF structures at high densities typical of recommended processing conditions and can only be eliminated by careful selection of processing parameters. Data constrained modelling, which uses the materials’ properties, was used for generating 3D representations of the complex structure surrounding LOF pores from X-ray CT datasets.

Metal Additive Manufacturing by Powder Blown Beam Deposition Process

Additive Manufacturing (AM) is a tool less manufacturing process for building complex components layer by layer. Powder based AM techniques are used for producing porous and dense parts or products by Powder Bed Fusion (PBF) and powder blown Beam Deposition (BD) processes respectively suitable for different applications. The present review is mainly focused on the commercially available technology of powder blown Beam Deposition (BD) process for producing fully dense parts, and functionally graded materials used in automotive, aerospace, defense, and nuclear reactors. The properties of BD parts and comparison of the properties of BD parts with Selective Laser Melting (SLM), casting, and Acram's Electron Beam Melting (EBM) parts are presented. This paper provides an insight into the microstructural characteristics and mechanical properties of parts produced by BD process. A brief discussion is presented on challenging issues and applications of BD process. An attempt is made to present available and under development AM testing standards used to evaluate the properties of AM parts. This review also focused on porous parts produced by BD process for medical applications, and metal foil based BD process. Here, new developments in AM process like hybrid manufacturing and 4D printing are also discussed.

Three-Dimensional Additively Manufactured Microstructures and Their Mechanical Properties

Metal additive manufacturing (AM) allows for the freeform creation of complex parts. However, AM microstructures are highly sensitive to the process parameters used. Resulting microstructures vary significantly from typical metal alloys in grain morphology distributions, defect populations and crystallographic texture. AM microstructures are often anisotropic and possess three-dimensional features. These microstructural features determine the mechanical properties of AM parts. Here, we reproduce three “canonical” AM microstructures from the literature and investigate their mechanical responses. Stochastic volume elements are generated with a kinetic Monte Carlo process simulation. A crystal plasticity-finite element model is then used to simulate plastic deformation of the AM microstructures and a reference equiaxed microstructure. Results demonstrate that AM microstructures possess significant variability in strength and plastic anisotropy compared with conventional equiaxed microstructures.

Quasi-Static Characterization of Polyamide-Based Discontinuous CFRP Manufactured by Additive Manufacturing and Injection Molding

Generating serial components via additive manufacturing (AM) a deep understanding of process-related characteristics is necessary. The extrusion-based AM called fused layer manufacturing (FLM), also known as fused deposition modeling (FDM™) or fused filament fabrication (FFF) is an AM process for producing serial components. Improving mechanical properties of AM parts is done by adding fibers in the raw material to reinforce the polymer. The study aims to create a more detailed comprehension of FLM and process-related characteristics with their influence on the composite.Thereby, a short carbon fiber-reinforced polyamide (CarbonX™ Nylon, 3DXTECH, USA) with 12.5 wt.‑% fiber content, 7 μm fiber diameter, and 150 to 400 µm fiber length distribution was investigated. To separate process-related characteristics of FLM, reference specimens were fabricated via injection molding (IM) with single-batch material. For the mechanical characterization, quasi-static tensile tests were carried out in accordance to DIN 527‑2. Quality assessment including void content and void distribution was performed via micro-computed tomography (CT).The mechanical characterization clarifies effects on mechanical properties depending on process-related characteristics of FLM. CT scans show higher void contents of FLM specimens compared to IM specimens and void orientation dependent on printing direction. FLM shows process-related characteristics which generally strengthen mechanical properties of polymers. Nevertheless, tensile strength of FLM specimens decrease by more than 28% compared to quasi-homogenous IM specimens.

Manipulating magnetic anisotropy in fused filament fabricated parts via macroscopic shape, mesoscopic infill orientation, and infill percentage

The application space for three-dimensional (3D) printing, such as fused filament fabrication (FFF), has grown significantly through the use of high-performance composite materials. While the mechanical, thermal, optical, and electrical properties of additive manufacturing (AM) polymer composites are being actively studied, the magnetic properties of AM parts have seen much less attention. Prior research has shown that the structural print settings for FFF influence the magnetic properties of the printed part (Bollig et al., 2017). However, the structural hierarchy present in the FFF process complicates a simple analysis of how these magnetic differences arise. Here, a magnetic filament consisting of polylactic acid (PLA) polymer and 40 wt.% iron was used to print a variety of samples to investigate how the macroscopic sample shape and the mesoscopic infill orientation and infill percentage affects the magnetic properties. The array of samples systematically covered different aspect ratios (length:width), edge contours (rectangular vs. ellipsoidal), two infill orientations (long axis alignment vs. short axis alignment), and varying infill percentages. The key results show that the highest magnetic susceptibility was seen for magnetic fields applied parallel to the infill orientation. The macroscopic geometry increased the magnetic susceptibility parallel to the long axis of the sample. Lastly, certain factors, such as edge contours and infill percentage, only affected the magnetic susceptibility when the magnetic field was applied transverse to the infill orientation, but had no effect when field was applied along the infill direction. Elucidating how the part shape, infill orientation, and infill percentage affects the magnetic properties of AM parts will help the community better understand how an FFF process can be utilized to make optimal magnetic components, such as transformer cores, electric motors, and electromagnetic interference shielding.

Analysis and Numerical Simulation of the Structural Performance of Fused Deposition Modeling Samples With Variable Infill Values

The prediction of the structural performance of additive manufacturing (AM) parts has become one of the main challenges to boost the use of AM in industry. The structural properties of AM are very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. While AM experimental studies are common in the literature, a limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches, such as the finite element method (FEM); however, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication. In this paper, the analysis and numerical simulation of the structural performance of fused deposition modeling (FDM) samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and polylactic acid (PLA) material. These samples were measured and modeled in a computer-aided design (CAD) system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally, the experimental and numerical results were compared and conclusions drawn.

Materials for additive manufacturing

Critical to the selection requirements for additive manufacturing (AM) is the need for appropriate materials. Materials requirements for AM include the ability to produce the feedstock in a form amenable to the specific AM process, suitable processing of the material by AM, capability to be acceptably post-processed to enhance geometry and properties, and manifestation of necessary performance characteristics in service. As AM has matured, specific classes of material have become associated with specific AM processes and applications. This paper gathers this information for each of the seven categories of ISO/ASTM AM categories. Polymers, metals, ceramics and composites are considered. Microstructural features affecting AM part properties are listed. Service properties of AM parts are described, including physical, mechanical, optical and electrical properties. An additive manufacturability index is proposed.