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CoCrW can be produced using Additive Manufacturing (AM), while casting methods are commonly used for applications such as dental prostheses. However, rapid heating and cooling during AM production can lead to internal defects, micro-cracks, and shrinkage. Micro-milling can help enhance the material's structure and impart micro-scale properties. This study aimed to investigate the micro-milling properties of CoCrW products manufactured using AM and compare them with materials produced by casting. Numerical models and experimental studies were conducted to examine the differences. Results showed that CoCr alloys produced with AM exhibited 25%–30% lower burr formations, while CoCrW produced by casting had 2%–5% lower surface roughness. Micro-milling experiments demonstrated that a feed rate of 2.5 μm/tooth resulted in 35%–40% more burr formation and surface roughness compared to a feed rate of 5 µm/tooth in both SLM and casting methods, attributed to the cutting edge radius. The cutting temperature and top burr height were analyzed using finite element simulations and experimental methods. It was observed that the maximum temperature in CoCrW produced by casting was 6%–15% higher than that in the SLM method. The finite element analyses and experiments revealed a difference of 4%–7% in maximum temperatures and top burr height. [ABSTRACT FROM AUTHOR]

Purpose: The nickel-based alloys Inconel 625 and Inconel 718 stand out due to their high strength and corrosion resistance in important industries like aerospace, aviation and automotive. Even though they are widely used, current techniques of producing materials that are difficult to cut pose several problems from a financial, ecological and even health perspective. To handle these problems and acquire improved mechanical and structural qualities, laser powder bed fusion (LPBF) has been widely used as one of the most essential additive manufacturing techniques. The purpose of this article is to focus on the state of the art on LPBF parts of Inconel 625 and Inconel 718 for microstructure, mechanical behavior and postprocessing. Design/methodology/approach: The mechanical behavior of LPBF-fabricated Inconel is described, including hardness, surface morphology and wear, as well as the influence of fabrication orientation on surface quality, biocompatibility and resultant mechanical properties, particularly tensile strength, fatigue performance and tribological behaviors. Findings: The postprocessing techniques such as thermal treatments, polishing techniques for surface enhancement, mechanical and laser-induced peening and physical operations are summarized. Originality/value: The highlighted topic presents the critical aspects of the advantages and challenges of the LPBF parts produced by Inconel 718 and 625, which can be a guideline for manufacturers and academia in practical applications. [ABSTRACT FROM AUTHOR]

In high-tech areas such as nuclear fusion, aerospace, and high-performance tools, tungsten and its alloys are indispensable due to their high melting point, low thermal expansion, and excellent mechanical properties. The rise of Additive Manufacturing (AM) technologies, particularly Laser Powder Bed Fusion (L-PBF), has enabled the precise and rapid production of complex tungsten parts. However, cracking and densification remain major challenges in printing tungsten samples, and considerable efforts have been made to study how various processing conditions (such as laser power, scanning strategy, hatch spacing, scan speed, and substrate preheating) affect print quality. In this review, we comprehensively discuss various critical processing parameters and the impact of oxygen content on the control of the additive manufacturing process and the quality of the final parts. Additionally, we introduce additive manufacturing-compatible W materials (pure W, W alloys, and W-based composites), summarize the differences in their mechanical properties, densification, and microstructure, and further provide a clear outlook for developing additive manufactured W materials. [ABSTRACT FROM AUTHOR]

Due to its lightweight, high strength, good machinability, and low cost, aluminum alloy has been widely used in fields such as aerospace, automotive, electronics, and construction. Traditional manufacturing processes for aluminum alloys often suffer from low material utilization, complex procedures, and long manufacturing cycles. Therefore, more and more scholars are turning their attention to the laser powder bed fusion (LPBF) process for aluminum alloys, which has the advantages of high material utilization, good formability for complex structures, and short manufacturing cycles. However, the widespread promotion and application of LPBF aluminum alloys still face challenges. The excellent printable ability, favorable mechanical performance, and low manufacturing cost are the main factors affecting the applicability of the LPBF process for aluminum alloys. This paper reviews the research status of traditional aluminum alloy processing and LPBF aluminum alloy and makes a comparison from various aspects such as microstructures, mechanical properties, application scenarios, and manufacturing costs. At present, the LPBF manufacturing cost for aluminum alloys is 2–120 times higher than that of traditional manufacturing methods, with the discrepancy depending on the complexity of the part. Therefore, it is necessary to promote the further development and application of aluminum alloy 3D printing technology from three aspects: the development of aluminum matrix composite materials reinforced with nanoceramic particles, the development of micro-alloyed aluminum alloy powders specially designed for LPBF, and the development of new technologies and equipment to reduce the manufacturing cost of LPBF aluminum alloy. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) process has a great ability to produce complex AlSi10Mg 3D components with uncommon degrees of freedom for broad span of applications in different industries. Presence of the microstructural imperfections such as porosity, dependent on the parameters of the process can be detrimental to the printed products for different engineering applications. Parameters of the process and different post-processing heat and surface treatments are recognized for decrease of the occurrence of microstructural defects and for the improvement of the mechanical properties. The influence of laser power by applying four different laser speeds at one layer thickness with a constant hatch distance, on the microstructure and microhardness of the AlSi10Mg alloy was examined in this paper. The goal of the research was to determine whether increasing the laser speed will have a significant impact on the change in microstructure and the appearance of porosity in the tested samples. [ABSTRACT FROM AUTHOR]

In recent years, the field of mandibular reconstruction has made great strides in terms of hardware innovations and their clinical applications. There has been considerable interest in using computer-aided design, finite element modelling, and additive manufacturing techniques to build patient-specific surgical implants. Moreover, lattice implants can mimic mandibular bone's mechanical and structural properties. This article reviews current approaches for mandibular reconstruction, their applications, and their drawbacks. Then, we discuss the potential of mandibular devices with lattice structures, their development and applications, and the challenges for their use in clinical settings. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing is a developing technique with numerous advantages and challenges to overcome. As with all manufacturing techniques, the specific raw materials and processing parameters used have a profound influence on microstructures and the resulting behavior of materials. It is important to understand the relationship between processing and microstructures of Ti to advance knowledge of Ti-alloys in the additive field. In this study, a face-centered cubic (FCC) phase was found in grade 2 commercially pure titanium specimens, additively manufactured with directed energy deposition in an argon atmosphere. Two scanning speeds (500 and 1000 mm/min) and three scanning patterns (cross-hatched and unidirectional patterns) were investigated. Electron backscatter diffraction and energy-dispersive X-ray spectroscopy were used for microstructural and compositional analysis. Inverse pole figure, phase, and kernel average misorientation (KAM) maps were analyzed in this work. Larger amounts of the FCC phase were found in the unidirectional scanning patterns for the slower scanning speed, while the cross-hatched pattern for both scanning speeds showed a lower amount of FCC. Higher KAM averages were present in the faster scanning speed specimens. According to EDS scans, small amounts of nitrogen were uniformly distributed throughout the specimens, leading to the possibility of interstitial content as a contributing factor for development of the observed FCC phase. However, there is no clear relationship between nitrogen and the FCC phase. The formation of this FCC phase could be connected to high densities of crystalline defects from processing, plastic deformation, or the distribution of interstitials in the AM structure. An unexpected Kurdjumow–Sachs-type orientation relationship between the parent beta phase and FCC phase was found, as 110 B C C ∥ 111 F C C , 111 B C C ∥ 110 F C C . [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) processes have emerged as alternatives for the production of grinding tools. This article addresses a comprehensive overview on the historical-scientific evolution of the AM production of grinding/abrasive tools and provides future trends in the field. Bibliometric and systematic reviews of the literature verified the technological frontiers of each AM method, indicating current possibilities and potential gaps for future perspectives. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM) is utilized to fabricate continuous fiber‐reinforced thermoplastic composites (CFRTPCs) and can be considered an alternative to conventional processes. In present study, the specimens are 3D printed in Markforged Mark Two composite 3D printer by considering Onyx as matrix material and fiberglass as reinforcing material. Thermal gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) of Onyx and fiberglass materials are done to investigate their thermal stability and composition. The effect of infill pattern and fiber orientation on tensile and drop impact properties are examined. The TGA results show that the initial decomposition in Onyx is higher compared to fiberglass due to more evaporation of moisture content in Onyx. The FTIR analysis confirmed that the spectrum for both materials is same within the range of wave number from 4000 to 1500 cm−1. The tensile test results represent that the specimen with triangular infill pattern and 0°/90° fiber orientation resulted in maximum tensile strength of 148.01 MPa and the drop impact test results showed that the triangular infill pattern with 0°/90° fiber orientation absorbs maximum impact energy which is 14.90% and 8.98% higher compared to honeycomb and rectangular pattern respectively. Further, the fracture behavior study is carried out based on the optical images of fractured specimens. [ABSTRACT FROM AUTHOR]

Industry 5.0 combines automation/digitalization with human capabilities to create a more intuitive, interactive, and sustainable working environment. Additive manufacturing, widely known as 3D printing, is a key technology used to increase customization and efficiency and reduce waste in manufacturing. Industry 5.0 enables manufacturers to create environmentally sustainable and consumer-centric products. However, there is a lack of studies on the introduction of AM technologies to Industry 5.0. The present study investigates the use of additive manufacturing for the fabrication of metallic parts/assemblies and the correlation between human-centric technologies, additive manufacturing, and environmental sustainability. Effective communication between these components is the key to achieving the goals of Industry 5.0, and the important parameters are shown in this article. The present work is focused on an overview and the impact of the futuristic subdivision of additive manufacturing applied to the fabrication of metallic parts/assemblies, more specifically, the 3D printing of challenging alloys or composites (such as copper alloys and/or composites with hard particles). [ABSTRACT FROM AUTHOR]

Titanium alloys are extensively used in various industries due to their excellent corrosion resistance and outstanding mechanical properties. However, titanium alloys are difficult to machine due to their low thermal conductivity and high chemical reactivity with tool materials. In recent years, there has been increasing interest in the use of titanium components produced by additive manufacturing (AM) for a range of high-value applications in aerospace, biomedical, and automotive industries. The machining of additively manufactured titanium alloys presents additional machining challenges as the alloys exhibit unique properties compared to their wrought counterparts, including increased anisotropy, strength, and hardness. The associated higher cutting forces, higher temperatures, accelerated tool wear, and decreased machinability lead to an expensive and unsustainable machining process. The challenges in machining additively manufactured titanium alloys are not comprehensively documented in the literature, and this paper aims to address this limitation. A review is presented on the machining characteristics of titanium alloys produced by different AM techniques, focusing on the effects of anisotropy, porosity, and post-processing treatment of additively manufactured Ti-6Al-4V, the most commonly used AM titanium alloy. The mechanisms resulting in different machining performance and quality are analysed, including the influence of a hybrid manufacturing approach combining AM with conventional methods. Based on the review of the latest developments, a future outlook for machining additively manufactured titanium alloys is presented. [ABSTRACT FROM AUTHOR]

The efficiency of the fabrication and the cost of feedstock materials are important constraining factors for a wider application of the laser powder bed fusion (LPBF) process in the industry. Therefore, it is necessary to investigate the feasibility of using different particle size distributions (PSD) combined with higher layer thickness for achieving higher building efficiency and cost-effectiveness. This paper focuses on the effect of PSD (0–53, 15–53, 15–75, and 15–105 μm) on the print quality and mechanical properties of the LPBF-processed Ti-6Al-4V at a layer thickness of 60 μm. The results show that volumetric energy density (VED) range, which allows the coarse powder to reach full density, becomes relatively narrower but is still capable of producing fully dense parts when the parameters are properly adjusted. Among the fully dense specimens, the surface roughness varies slightly with the increase of VED and PSD. In the case of proper parameter selection, specimens made of coarse powder can still achieve low surface roughness. Only slight differences in mechanical performance are found for specimens produced using different PSD powders as they have almost identical microstructures. The issue of the anisotropic mechanical properties of the as-built specimens is resolved after annealing treatment at 800 °C for 2 h. This study provides a guideline for producing high-quality Ti-6Al-4V parts using a higher layer thickness and coarser powders. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber reinforced polymer composite 3D printing has drawn more attention due to its ability to manufacture composite structures with complex shapes. The surface treatment of CF is necessary to improve the combination between carbon fiber (CF) and matrix. In this work, polyurethane with nano‐SiO2 (PU/SiO2) was used to size CF to enhance the compatibility of CF and nylon 6 (PA6). The chemistry and morphology of the CF were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The interface strength between CF and PA6 was tested by the fiber pull‐out test, and eventually obtained optimized concertation of PU/SiO2 sizing agents (with 25 wt% PU and 0.4 wt% nano‐SiO2). The results show that compared with untreated CF, the interfacial shear strength (IFSS) of CF and PA6 after sizing increased by 316.93%. In addition, several CF/PA6 composite specimens printed by a homemade composite 3D printer were used to do mechanical tests. The results show that the flexural strength increased by 33.87%, the tensile strength increased by 20.75%, and the interlaminar shear strength (ILSS) increased by 66.54%. [ABSTRACT FROM AUTHOR]

Additive manufacturing has new revolutionary potential for carbon fiber‐reinforced polymers (CFRPs). Additive manufacturing of CFRPs combines the advantages of additive manufacturing such as customization, minimal wastage, low cost, fast prototyping and rapid manufacturing with high specific strength of carbon fiber. This article delivers a comprehensive review of additive manufacturing of short and continuous CFRPs. The article presents insight into different additive manufacturing techniques with an overview of commercially available methods for manufacturing short and continuous CFRPs. This review also includes mechanical characterization and analytical techniques discussed in the literature for CFRPs. The robust applications of short and continuous CFRPs in biomedical, electronics, and aerospace would highlight the importance of research and development in this field. In the end, drawbacks, recent innovations, and the future research directions underline the gap between research and commercialization of additive manufacturing of short and continuous CFRPs. [ABSTRACT FROM AUTHOR]

In this research, the multiphysics modelling was implemented for laser powder bed fusion (L-PBF) process simulation to study the influence of layer thickness on thermo-fluid behavior, and single tracks formation during L-PBF process of AISI H13 steel. The influence of energy input adjustment on forming characteristics of single tracks in various layer thickness were examined and predicted in this work. The discrete element method and the computational fluid dynamic model were implemented to simulate the temperature distribution, and molten metal flow behavior during L-PBF process. The results indicated that the layer thickness has more effect on the depth of single track than width of single track. Due to high thermal conductivity between solid substrate and powder bed at the lowest layer thickness of 30 µm, the shallowest single tracks penetration depth was formed. The adjustment of energy input including laser power and scanning speed is an effective method to obtain the sufficient depth of penetration at 30 µm, 70 µm, and 100 µm layer thicknesses. The single track depth with the layer thicknesses of 30 µm reduced around 27 µm when laser power was decreased from 200 to 125 W and 28 µm and the scanning speed was increased from 1000 to 1600 mm/s. At 70 µm layer thickness the depth of single track was increased around 20 µm when the laser power was elevated from 200 to 250 W, and 19 µm when scanning speed was reduced from 1000 to 800 mm/s. Moreover, from this study the numerical simulation result revealed the layer thickness adjustment range between 50 and 70 µm with particle sizes used in this research provided the single track with continuous, regular sizes and sufficient penetration depth when medium energy density is used. [ABSTRACT FROM AUTHOR]

The present study aims to analyse of the role of volumetric energy density (VED) in the achievement of denser titanium alloy (Ti6Al4V) through the use of Laser based powder bed fusion (L-PBF) process. Rectangular blocks were fabricated with five different VEDs, namely, 35.07 J/mm3, 40.46 J/mm3, 44.19 J/mm3, 55.11 J/mm3 and 60.45 J/mm3. A highly intensified laser beam causes a faster cooling rate resulting in excessive formation of unstable needle-like martensite (α') phases inside the columnar beta (β) grains. Reduction in scan speed from 990 to 630 mm/sec with constant laser power as 250 W triggered the formation of keyhole pores. Also, a similar kind of observation was noted when the scan speed was reduced from 1270 to 850 mm/sec with constant laser power of 370 W. The sample fabricated with a VED of 44.19 J/mm3 resulted in a minimum fraction of porosity, i.e. 0.04%.The sample fabricated with a VED 44.19 J/mm3 was subjected to solution heat treatment (HT) at 950 °C/1 h and 1050 °C/1 h, i.e. below and above the β transition temperature for the achievement of stable equilibrium microstructure.Solution HT at 950 °C resulted in the growth of thin and thick needles of Widmanstätten α phases followed by water quenching (WQ) and air cooling (AC), respectively. The columnar β grains were disintegrated at 1050 °C leading to the equiaxed grain boundary α along with newly formed α' phases after WQ and lamellar α phases after AC. The findings of the study showed the role of energy densities and post L-PBF HT in the achievement of stable microstructure on Ti6Al4V alloy. [ABSTRACT FROM AUTHOR]

In laser-based powder bed fusion of metals (PBF-LB/M), residual oxygen in the processing atmosphere is regarded as disruptive and disadvantageous for the manufacturing process and the resulting component properties. A novel approach to eliminate residual oxygen is to add small amounts of silane to the argon process gas. Silane eliminates residual oxygen and forms SiO2 nanoparticles, which in turn can be incorporated into the powder during the process. It is therefore necessary to evaluate the influence of these nanoparticles admixed to the metal powder. In this work, Ti-6Al-4V powder was modified with pyrogenic SiO2 nanoparticles generated by the reaction of a silane argon gas mixture with ambient air. Modified and unmodified powder was analyzed and processed using statistically designed experiments. An improvement of the flow rate according to DIN EN ISO 4490 (from 33.3 to 32.5 s/50 g) and increase of apparent density according to DIN EN ISO 3923 (from 2.52 to 2.58 g/cm3) could be observed after powder modification. No statistically significant effects of the modification on roughness, porosity, and hardness were found. The results demonstrate that powder modification using silane can lead to enhanced flowability without affecting the PBF-LB processing window of Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

The laser powder bed fusion (L-PBF) process is a powder-based additive manufacturing process that can manufacture complex metallic components. However, when the metallic components are fabricated with the L-PBF process, they frequently encounter the residual stress and distortion that occurs due to the cyclic of rapid heating and cooling. The distortion detrimentally impacts the dimensional and geometrical accuracy of final built parts in the L-PBF process. The purpose of this research was to explore and predict the distortion of Ti-6Al-4V components manufactured using the L-PBF process by using numerical modeling in Simufact Additive 2020 FP1 software. Firstly, the numerical model validation was conducted with the twin-cantilever beam part. Later, studies were carried out to examine the effect of component sizes and support-structure designs on the distortion of tibial component produced by the L-PBF process. The results of this research revealed a good agreement between the numerical model and experiment data. In addition, the platform was extended to predict the distortion in the tibial component. Large distortion arose near the interface between the tibial tray and support structure due to the different stiffness between the solid bulk and support structure. The distortion of the tibial component increased with increasing component size according to the surface area of the tibial tray, and with increasing thickness of the tibial tray. Furthermore, the support-structure design plays an important role in distortion reduction in the L-PBF process. For example, the maximum distortion of the tibial component was minimized up to 44% when a block support-structure design with a height of 2.5 mm was used instead of the lattice-based support. The present study provides useful information to help the medical sector to manufacture effective medical components and reduce the chance of part failure from cracking in the L-PBF process. [ABSTRACT FROM AUTHOR]

The microstructure, static, and fatigue mechanical properties of laser powder bed fused (LPBF) Ti-6Al-4V components subjected to three different post-processing treatments (PTs) are compared. The first treatment includes stress relief (SR) and beta-phase annealing (BA) heat treatments, the second one includes SR, beta-solution (BST) and over aging (OA) heat treatments, and the third procedure is a combination of hot isostatic pressing (HIP) and BST + OA. It was demonstrated that the three PTs led to the decomposition of α' martensite inherited from the LPBF process and the formation of variable α + β structures. The SR + BA treatment forms a basket weave structure having an average α lamellae width of ~3 µm and surrounded by ~1 µm-sized zones of segregated β phase (4.6–5.2% β phase content) and globalized α phase (~10 µm in size) inside prior columnar β grains (~100 µm in width). The SR + BST + OA treatment forms semi-equiaxed α grains (~300 µm) containing colonies (~50 µm) of parallel-oriented α plates (~6 µm), and β phase (5.8–7.5%) in the interplate spacing. The HIP + BST + OA treatment leads to the formation of large grains (~500 µm) with both basket weave and colony (~40 µm) α structures containing α plates (1.1–4.2 µm) and β phase (5–7.1%). To compare the impact of these PTs on the mechanical properties of LPBF components, they were subjected to static and fatigue tensile testing at room temperature. The best combination of mechanical properties (yield strength ~920 MPa, ultimate strength ~1000 MPa, elongation to break ~22.5%, and fatigue strength ~600 MPa, 107 cycles) was obtained in the case of SR + BA specimens. These results demonstrate that an adequate thermal treatment, such as SR + BA, of the LPBF Ti64 components, could be a valuable and less expensive alternative to the established HIP + BST + OA treatment procedure when fatigue life is the main concern. [ABSTRACT FROM AUTHOR]

The laser-based powder bed fusion of metals (PBF-LB/M) offers a variety of advantages over conventional processing techniques and the possibility to recycle and reuse powder increases its sustainability. However, the process and resulting part properties are influenced by a variety of factors including powder recycling grade and residual oxygen content of the process atmosphere. Especially in terms of reactive materials like Ti-6Al-4V, oxidation during processing and recycling determines process stability and reproducibility. This work therefore focusses on the influence of the conventionally varied processing parameters as well as atmosphere residual oxygen content process and powder recycling on the microstructure and mechanical properties. For this purpose, the design of experiments approach is used and by evaluation of regression models, effect sizes and interactions are given. Additionally, two different etching techniques were employed to reveal different aspects of the microstructure. While no significant influence of powder recycling and residual oxygen on the microstructure could be observed, they both significantly influence the mechanical properties. A maximum hardness of 470 HV0.1, a maximum ultimate tensile strength of 1252.3 MPa, and a maximum elongation at break of 17.8 % were obtained. The results demonstrate the importance of the processing atmosphere's residual oxygen content and of taking into account the changing powder characteristics during recycling as well as its effect on the part properties. [ABSTRACT FROM AUTHOR]

This work focuses on the effect of different heat treatments on the Ti-6Al-4V alloy processed by means of electron beam melting (EBM). Super β-transus annealing was conducted at 1050 °C for 1 h on Ti-6Al-4V samples, considering two different cooling paths (furnace cooling and water quenching). This heat treatment induces microstructural recrystallization, thus reducing the anisotropy generated by the EBM process (columnar prior-β grains). Subsequently, the annealed furnace-cooled and water-quenched samples were aged at 540 °C for 4 h. The results showed the influence of the aging treatment on the microstructure and the mechanical properties of the annealed EBM-produced Ti-6Al-4V. A comparison with the traditional processed heat-treated material was also conducted. In the furnace-cooled specimens consisting of lamellar α+β, the aging treatment improved ductility and strength by inducing microstructural thickening of the α laths and reducing the β fraction. The effect of the aging treatment was also more marked in the water-quenched samples, characterized by high tensile strengths but limited ductility due to the presence of martensite. In fact, the aging treatment was effective in the recovery of the ductility loss, maintaining high tensile strength properties due to the variation in the relative number of α/α' interfaces resulting from α' decomposition. This study, therefore, offers an in-depth investigation of the potential beneficial effects of the aging treatment on the microstructure and mechanical properties of the EBM-processed super β-transus heat-treated Ti-6Al-4V alloy under different cooling conditions. [ABSTRACT FROM AUTHOR]

Selective laser melting is a frequently used, powder bed fusion additive manufacturing technology for producing metallic parts. However, appropriate surface quality cannot be achieved, so post-processing is often necessary. Subsequent machining of surfaces serves multiple objectives such as improvement of dimensional accuracy, changing surface roughness and modification of the residual stress state for higher surface hardness. Beyond its several advantageous properties, Ti6Al4V material has, as its weaknesses, low tribological behavior and wear resistance. Sliding friction burnishing is a conventional chipless and coolant-free environmentally conscious technology for surface modification that is appropriate for simultaneously decreasing surface roughness and increasing surface hardness. Until now, there has been a research gap regarding the diamond burnishing of selective laser melted Ti6Al4V parts. In this study, we investigated how the surface roughness of selective laser melted parts can be modified via sliding friction burnishing. 2D and 3D characteristics of surface roughness were measured by a chromatic roughness measuring device. Indices of surface roughness improvement were defined and studied as a function of selective laser melting parameters. Optimal manufacturing parameters of laser power—P = 280 W and scanning speed u = 1200 mm/s—for effective surface improvement via burnishing are proposed. [ABSTRACT FROM AUTHOR]

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Metal additive manufacturing, which uses a layer-by-layer approach to fabricate parts, has many potential advantages over conventional techniques, including the ability to produced complex geometries, fast new design part production, personalised production, have lower cost and produce less material waste. While these advantages make AM an attractive option for industry, determining process parameters which result in specific properties, such as the level of porosity and tensile strength, can be a long and costly endeavour. In this review, the state-of-the-art in the control of part properties in AM is examined, including the effect of microstructure on part properties. The simulation of microstructure formation via numerical simulation and machine learning is examined which can provide process quality control and has the potential to aid in rapid process optimisation via closed loop control. In-situ monitoring of the AM process, is also discussed as a route to enable first time right production in the AM process, along with the hybrid approach of AM fabrication with post-processing steps such as shock peening, heat treatment and rolling. At the end of the paper, an outlook is presented with a view towards potential avenues for further research required in the field of metal AM. [ABSTRACT FROM AUTHOR]

In this study, the influence that porosities play on the mechanical properties of Ti-6Al-4V parts fabricated by laser powder bed fusion (LPBF) was investigated with the aim of improving process efficiency of the LPBF process by establishing the resulting trade-offs to component quality. It was found that build times can be substantially reduced by using higher layer thickness parameters without a significant detriment to mechanical properties. Where porosities formed, spherical pores tend to have a marginal effect on Young's modulus, yield strength, tensile strength, and uniform elongation as these properties can be approximated linearly using the rule of mixtures assuming null strength pores. However, such pores were found to be otherwise more detrimental to total elongation and toughness. Conversely, lack of fusion pores are extremely detrimental and should be avoided. Thus, it is proposed that when building a component, different process parameters can be used at different regions of the component to maximize process efficiency without compromising its overall function. For instance, for surfaces, a highly optimized parameter set with lower layer thickness can be used. At regions with minimal stress distribution during service, a large layer thickness parameter set where the resulting mechanical properties is sufficient can be used. [ABSTRACT FROM AUTHOR]

A hybrid powder of Ti6Al4V, which consists of 50 wt% plasma atomised (PA) spherical and 50 wt% hydride-dehydride (HDH) irregular-shaped powder with a flowability of 36.5 s, is projected as the raw materials in this research. In addition, Ti6Al4V (Gr.23) plasma atomised 100 wt% spherical powder was used as the reference powder with a flowability of 28 s to facilitate the tensile property discussion. It was found that the powder flowability is the crucial parameter governing the tensile properties of fabricated specimens. It was shown that the decrease in powder flowability (36.5 s) resulted in increases in susceptibility to the formation of a lack of fusion defects with dropped tensile properties. The microstructure of the fabricated Ti6Al4V alloy features the formation of prior β grain boundaries and an alpha prime (α′) martensite. Furthermore, no intermetallic aluminide phase (Ti3Al) precipitations in grain boundaries were detected through energy-dispersive X-ray spectroscopy analysis. [ABSTRACT FROM AUTHOR]

Additive manufacturing of sophisticated 3D nanoscale objects commonly uses femtosecond lasers to photopolymerize a light‐sensitive resin using multi‐photon absorption. This nonlinear process provides high accuracy and flexibility in advanced 3D fabrication; however, it typically has limited throughput and high cost. This work makes use of a one‐photon‐based dosage‐nonlinearity to fabricate 3D nanostructures, demonstrating a cost‐effective method for 3D nanolithography using a low‐cost 405 nm continuous‐wave diode laser. This dosage‐nonlinearity is achieved by using controlled depletion of photo‐initiation species in an environment containing inhibiting species. By controlling multiple competing processes, the undesired dose accumulation outside the writing voxel is stopped, and thereby this method creates a confined writing voxel in space. A multiphysics model is developed to numerically study the one‐photon nonlinear photopolymerization process, which is compared with experimental results. [ABSTRACT FROM AUTHOR]

A promising approach to address the mismatch of bone and implant stiffness, leading to the stress-shielding phenomenon, is the application of functionally graded materials with adjusted porosity. Although defect formation and porosity in laser-based powder bed fusion of metals (PBF-LB/M) are already widely investigated, so far there is little research on the influences and parameter interactions regarding the pore characteristics. This work therefore aims to provide an empirical process model for the generation of gas porosity in the PBF-LB process of Ti-6Al-4V. Parts with closed locally adjusted porosity of ∼ 6 % achieved through gaseous pores instead of lack of fusion defects or lattice structures were built by PBF-LB. Parameter variation and evaluation of relative density, pore size and sphericity was done in accordance with the design of experiments approach. A parameter set for maximum gas porosity (laser power of 189 W, scanning speed of 375 mm/s, hatch spacing of 150 μm) was determined for a constant layer thickness of 30 μm and a spot diameter of 35 μm. Tensile tests were conducted with specimens consisting of a core with maximum gas porosity or lack of fusion porosity, respectively, and a dense skin as well as fully dense specimens. Whereas lack of fusion defects can lead to significant reduction of stiffness of 32.2 %, the elastic modulus remained unchanged at 110.0 GPa when implementing spherical pores. Nevertheless, the found superior strength and ductility of specimens with gas porous core (> 1100 MPa and > 0.05 mm/mm, respectively) underline the advantages of adjusted porosity for the application in functionally graded materials and lightweight applications. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of metallic alloys offers a new avenue to print objects having complex geometries. This exclusive benefit of AM has made it an alternative route to conventional manufacturing. Importantly, additively manufactured (AMed) alloys often exhibit improved microstructures, which may provide better properties. The microstructure of an alloy can be tuned by controlling the processing parameters. This study includes an overview of the processing parameters that can influence the microstructural, mechanical, and corrosion properties of AMed alloys. Moreover, the effects of heat treatment on AMed alloys are also discussed. Among various processing parameters, it is observed that the laser power significantly influences the microstructure. The microstructures produced with high laser power are similar to heat-treated samples for 316L stainless steel (SS) and Ti6Al4V. Similarly, variation in scanning speed results in distinct morphology of grains in Ti6Al4V. Moreover, different AM processes, such as SLM and EBM, produce coarse and fine β grains, respectively, in Ti6Al4V. The fabrication of AlSi10Mg yields various sizes of melt pool due to different scanning strategies. Furthermore, mechanical properties such as microhardness is higher and the yield strength is lower for Ti6Al4V fabricated at lower laser power. The corrosion behavior of SLMed Ti6Al4V is different on the perpendicular and parallel planes to the build direction. Due to the increase in grain size after heat treatment, the corrosion resistance of AMed Ti6Al4V and AlSi10Mg is reduced. In contrast, heat treatment applied on 316L, Ti6Al4V, AlSi10Mg, and Inconel 718 is beneficial for mechanical properties. After the development of materials with optimized processing parameters, the research should be conducted on replacement of the wrought alloys with the AMed alloys. It is expected that new applications such as fuel cells and biomedical devices will utilize the AM technology to build parts in the recent future. [ABSTRACT FROM AUTHOR]

Ti6Al4V (Ti64) alloys manufactured by selective laser melting (SLM) are well known for their susceptibility to failure at a low ductility of less than 10% due to the formation of an (α′) martensitic structure. Annealing and solution treatments as post-heat treatments of α′ are considered a good way to improve the mechanical performance of SLM-manufactured Ti64 parts. In this research, the effect of heat treatment parameters such as temperature (850 °C and 1020 °C) and cooling rate (furnace and water cooling) on the microstructure and mechanical properties of the SLM Ti64 structure was investigated. It was shown that the tensile strength/ductility of the Ti64 alloy produced by SLM was determined by the post-heat treatment. The experimental results revealed that heat treatment at 850 °C followed by furnace cooling resulted in the best possible combination of ductility (13%) and tensile strength (σy = 932, σu = 986 MPa) with a microstructure consisting mainly of 78.71% α and 21.29% β. Heat treatment at 850 °C followed by water cooling was characterized by a reduction in hardness and the formation of predominantly α plus α′′ and a small amount of β. HT850WC exhibited yield and tensile strengths of about 870 and 930 MPa, respectively, and an elongation at fracture of 10.4%. Heat treatment at 1020 °C and subsequent cooling in the furnace was characterized by the formation of an α + β lamellar microstructure. In contrast, heat treatment at 1020 °C and subsequent water cooling formed semi-equiaxial β grains of about 170 µm in diameter with longer elongated α grains and basket-weave α′. Post-treatment at 1020 °C followed by furnace cooling showed high ductility with an elongation of 14.5% but low tensile strength (σy = 748, σu = 833 MPa). In contrast, post-treatment at 1020 °C followed by water cooling showed poor ductility with elongation of 8.6% but high tensile strength (σy = 878, σu = 990 MPa). The effect of aging at 550 °C for 3 h and cooling in a furnace on the microstructure and mechanical properties of the specimens cooled with water was also studied. It was found that aging influenced the microstructure of the Ti6Al4V parts, including β, α, and α″ precipitation and fragmentation or globularization of elongated α grains. The aging process at 550 °C leads to an increase in tensile strength and a decrease in ductility. [ABSTRACT FROM AUTHOR]

This work investigated the influence of process parameters on the densification, microstructure, and mechanical properties of a Ti–6Al–4V alloy printed by selective laser melting (SLM), followed by annealing heat treatment. In particular, the evolution mechanisms of the microstructure and mechanical properties of the printed alloy with respect to the annealing temperature near the β phase transition temperature were investigated. The process parameter optimization of SLM can lead to the densification of the printed Ti–6Al–4V alloy with a relative density of 99.51%, accompanied by an ultimate tensile strength of 1204 MPa and elongation of 7.8%. The results show that the microstructure can be tailored by altering the scanning speed and annealing temperature. The SLM-printed Ti–6Al–4V alloy contains epitaxial growth β columnar grains and internal acicular martensitic α′ grains, and the width of the β columnar grain decreases with an increase in the scanning speed. Comparatively, the printed alloy after annealing in the range of 750–1050 °C obtains the microstructure consisting of α + β dual phases. In particular, network and Widmanstätten structures are formed at the annealing temperatures of 850 °C and 1050 °C, respectively. The maximum elongation of 14% can be achieved at the annealing temperature of 950 °C, which was 79% higher than that of as-printed samples. Meanwhile, an ultimate tensile strength larger than 1000 MPa can be maintained, which still meets the application requirements of the forged Ti–6Al–4V alloy. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) additive manufacturing (AM) exhibits uncertainties, where variations in build quality are present despite utilizing the same optimized processing parameters. In this work, we identify the sources of uncertainty in SLM process by in-situ characterization of SLM dynamics induced by small variations in processing parameters. We show that variations in the laser beam size, laser power, laser scan speed, and powder layer thickness result in significant variations in the depression zone, melt pool, and spatter behavior. On average, a small deviation of only ~5% from the optimized/reference laser processing parameter resulted in a ~10% or greater change in the depression zone and melt pool geometries. For spatter dynamics, small variation (10 μ m , 11%) of the laser beam size could lead to over 40% change in the overall volume of the spatter generated. The responses of the SLM dynamics to small variations of processing parameters revealed in this work are useful for understanding the process uncertainties in the SLM process. [ABSTRACT FROM AUTHOR]

During the process of laser powder bed fusion (LPBF) printing, the energy of heat input have a great influence on the quality of fabricated specimens. In this paper, based on the heat transfer and metallurgical mechanism, a theoretical predicting model of the required laser energy to fabricate high-density LPBF components was established. The theoretical required laser energy density of AlSi10Mg, TC4 and 316L were calculated, which are 51.74 J/mm3, 104.48 J/mm3 and 69.28 J/mm3, respectively. By comparing with the experimental results in the references, it was found that the errors between them are within 10%. In addition, this article discussed the relationship between the VED and the specimen defects, and found that the changing in the VED will alter the types of specimen defects. [ABSTRACT FROM AUTHOR]