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The solar‐driven interface evaporation is one of the most promising technologies for desalination and wastewater purification. However, in the ebb and flow of the tide, water absorbed in the hydrophilic evaporator bottom would significantly change, leading to the shape deformation of the system and further failure of solar steam generation. Here it is reported that the moisture‐thermal stable and superhydrophilic alumina‐based ceramics can be fabricated by a selective laser sintering (SLS) 3D printing strategy. The printed alumina‐based ceramics possess superhydrophilicity. Along the side surface of the printed sample, a 5 µL water droplet can be fast absorbed in 14 ms. Most importantly, they can maintain stable and high evaporation efficiency even after being dried out for ten times, demonstrating the excellent physical resistance to continuous moisture‐thermal transition. Finally, the "I‐shaped" evaporators are printed with salt‐resistant ability, which can maintain a steady high evaporation efficiency in seawater and 20 wt% brine for long‐term steam generation process. The moisture‐thermal stable alumina‐based ceramics prepared in this work will provide inspiration for stable solar steam generation materials, and expand the development of 3D printing functional materials. [ABSTRACT FROM AUTHOR]

Manufacturing abrasion‐resistant superhydrophobic matters is challenging due to the fragile feature of the introduced micro‐/nanoscale surface roughness. Besides the long‐term durability, large scale at meter level, and 3D complex structures are of great importance for the superhydrophobic objects used across diverse industries. Here it is shown that abrasion‐resistant, half‐a‐meter scaled superhydrophobic objects can be one‐step realized by the selective laser sintering (SLS) 3D printing technology using hydrophobic‐fumed‐silica (HFS)/polymer composite grains. The HFS grains serve as the hydrophobic guests while the sintered polymeric network provides the mechanical strength, leading to low‐adhesion, intrinsic superhydrophobic objects with desired 3D structures. It is found that as‐printed structures remained anti‐wetting capabilities even after undergoing different abrasion tests, including knife cutting test, rude file grinding test, 1000 cycles of sandpaper friction test, tape test and quicksand impacting test, illustrating their abrasion‐resistant superhydrophobic stability. This strategy is applied to manufacture a shell of the unmanned aerial vehicle and an abrasion‐resistant superhydrophobic shoe, showing the industrial customization of large‐scale superhydrophobic objects. The findings thus provide insight for designing intrinsic superhydrophobic objects via the SLS 3D printing strategy that might find use in drag‐reduce, anti‐fouling, or other industrial fields in harsh operating environments. [ABSTRACT FROM AUTHOR]

Ceramic-based absorbing composite is irreplaceable in high-temperature conditions. This work has fabricated a novel biomass–derived porous SiCnw/SiC composite for structure–function integrated electromagnetic wave (EMW) absorption through selective laser sintering (SLS) 3D printing and carbothermal reduction. SLS processed the biomass-derived wood precursor with unique porous microstructures. The structure–function properties were controlled by changing the SiO carbothermal reduction temperatures, which facilitated the growth of SiC nanowires for effective EMW absorption. The 3D printed porous SiCnw/SiC composite shows efficient EMW absorption abilities with a minimum reflection loss of −49.01 dB and an effective absorption bandwidth of 5.1 GHz. The bulk density and flexural strength of porous SiCnw/SiC composite are respectively 0.73 ± 0.001 g/cm3 and 6.21 ± 0.66 MPa. Despite a high open porosity of 75.58 ± 0.31%, the porous SiCnw/SiC composite demonstrates excellent thermal conductivities of 3.21∼4.99 W/(m·K) and superior fire-resistant ability. The 3D printed SiCnw/SiC composite integrates structure and functions, indicating wide applications in specific harsh environments. [ABSTRACT FROM AUTHOR]

PLA(a biodegradable material) and HA(the main inorganic component) were used as research objects. In order to obtain the optimal parameters of SLS parts of composite materials, the SLS process of pure PLA was optimized firstly. It is found that the tensile strength of pure PLA prepared by SLS are over 23 MPa when the laser energy density range is as 0.040~0.075 J/mm2, and the highest strength is as 27.28 MPa. The PLA/HA composites with different HA contents were processed with laser energy density of 0.040 J/mm2, laser power of 12 W and scanning speed of 1 500 mm/s, to study the influences of HA contents on the microstructure and mechanics properties of PLA/HA composites. The experimental results show that the composite with 10% mass fraction HA has the best mechanics properties and micromorphology. The water contact angle tests also exhibit that the contact angles of the materials decrease from 69.52° to 57.96°, which indicate that the hydrophilicity of the materials is improved. [ABSTRACT FROM AUTHOR]

Purpose Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit cell topology is a significant factor that determines the mechanical property of porous scaffolds. Therefore, the purpose of this paper is to evaluate the effects of unit cell topology on the compression properties of porous Cobalt–chromium (Co-Cr) scaffolds fabricated by SLM using finite element (FE) and experimental measurement methods.Design/methodology/approach The Co-Cr alloy porous scaffolds constructed in four different topologies, i.e. cubic close packed (CCP), face-centered cubic (FCC), body-centered cubic (BCC) and spherical hollow cubic (SHC), were designed and fabricated via SLM process. FE simulations and compression tests were performed to evaluate the effects of unit cell topology on the compression properties of SLM-processed porous scaffolds.Findings The Mises stress predicted by FE simulations showed that different unit cell topologies resulted in distinct stress distributions on the bearing struts of scaffolds, whereas the unit cell size directly determined the stress value. Comparisons on the stress results for four topologies showed that the FCC unit cell has the minimum stress concentration due to its inclined bearing struts and horizontal arms. Simulations and experiments both indicated that the compression modulus and strengths of FCC, BCC, SHC, CCP scaffolds with the same cell size presented in a descending order. These distinct compression behaviors were correlated with the corresponding mechanics response on bearing struts. Two failure mechanisms, cracking and collapse, were found through the results of compression tests, and the influence of topological designs on the failure was analyzed and discussed. Finally, the cell initial response of the SLM-processed Co-Cr scaffold was tested through the in vitro cell culture experiment.Originality/value A focus and concern on the compression properties of SLM-processed porous scaffolds was presented from a new perspective of unit cell topology. It provides some new knowledge to the structure optimization of porous scaffolds for load-bearing bone implants. [ABSTRACT FROM AUTHOR]

This work evaluated the processibility of a low-isotacticity polypropylene (PP) powder by selective laser sintering (SLS), and systematically analyzed and compared the melting and crystallization characteristics, crystalline structure, tensile properties and thermo-mechanical properties of the PP specimens fabricated by SLS and injection molding (IM). The results show that the PP powder has a nearly spherical shape, smooth surfaces, appropriate particle sizes, a wide sintering window and a low degree of crystallinity, consequently indicating good SLS processibility. In SLS, the molten PP continues to maintain at a high part bed temperature until the whole manufacturing process finished, thus demonstrating a low cooling rate. This gives rise to a high degree of crystallinity, formation of γ phase and coarse microstructure. On the contrary, in IM, the fully molten PP is rapidly cooled down to room temperature after injection, and thus show a higher cooling rate and rapid crystallization, leading to a lower degree of crystallinity, absence of γ phase and finer microstructure. Owing to these differences in crystallization characteristics and crystalline structure mentioned above, the SLS PP parts exhibit higher tensile strengths, tensile moduli and storage moduli, but lower elongation at break, toughness and glass transition temperatures, compared with the IM counterparts. [ABSTRACT FROM AUTHOR]

Nanosilica was used to reinforce the selective laser sintering (SLS) parts of nylon-12. A dissolution-precipitation process was successfully developed to prepare a nanosilica/nylon-12 composite powder (containing 3 wt% nanosilica) for SLS process. The dispersion of nanosilica in the SLS specimens of the composite powder was examined by scanning electron microscope (SEM), and the effects of nanosilica on the thermal and mechanical properties of the SLS parts were investigated. The results show that: nanosilica disperses uniformly on a nano-scale level in the SLS parts of the composite powder; nanosilica has a heterogeneous nucleation effect on nylon-12; the composite powder has much higher thermal stability than neat nylon-12; the tensile strength, tensile modulus, and impact strength of the SLS specimens made from the composite powder are 20.9, 39.4, and 9.54% higher than those of neat nylon-12 SLS specimens, respectively, and the elongation at break decreases by about 3.65%. [ABSTRACT FROM AUTHOR]

Abstract: A dissolution–precipitation process was successfully developed to prepare nylon-12 coated carbon steel powders. The SEM and laser diffraction particle size analysis results show that the metal particles are well coated by nylon-12 resin; therefore, an effective method for preparing nylon-12 coated metal powders is provided. Green parts were formed from the coated powders by selective laser sintering (SLS) process, and when the nylon-12 content in the coated powder was 1.0wt% and the applied laser energy density was 0.06J/mm2, the SLS green parts had sufficient strengths for features as small as 0.1mm to be built and post-processed, and relatively high dimensional accuracy. The SLS green parts were post-processed by binder decomposition and epoxy resin infiltration, and the obtained epoxy-infiltrated parts have the dimensional errors in the X, Y and Z directions of −0.30, −0.32 and −0.25% respectively, and the bend strength, bend modulus, tensile strength and impact strength of 93.4MPa, 14.7GPa, 70.3MPa and 12.4MPa respectively. [Copyright &y& Elsevier]

Nickel-titanium alloys have been widely used in biomedical, aerospace and other fields due to their shape memory effect, superelastic effect, as well as biocompatible and elasto-thermal properties. Additive manufacturing (AM) technology can form complex and fine structures, which greatly expands the application range of Ni-Ti alloy. In this study, the development trend of additive manufactured Ni-Ti alloy was analyzed. Subsequently, the most widely used selective laser melting (SLM) process for forming Ni-Ti alloy was summarized. Especially, the relationship between Ni-Ti alloy materials, SLM processing parameters, microstructure and properties of Ni-Ti alloy formed by SLM was revealed. The research status of Ni-Ti alloy formed by wire arc additive manufacturing (WAAM), electron beam melting (EBM), directional energy dedication (DED), selective laser sintering (SLS) and other AM processes was briefly described, and its mechanical properties were emphatically expounded. Finally, several suggestions concerning Ni-Ti alloy material preparation, structure design, forming technology and forming equipment in the future were put forward in order to accelerate the engineering application process of additive manufactured Ni-Ti alloy. This study provides a useful reference for scientific research and engineering application of additive manufactured Ni-Ti alloys. [ABSTRACT FROM AUTHOR]

Additive manufactured porous SiC is a promising material applied in extreme conditions characterised by high temperatures, chemical corrosion, and irradiation etc. However, residual Si's existence deteriorates its performance and limits its application in harsh environments. In this study, B4C was introduced into the selective laser sintering process of SiC, and its effects on forming ability, pore parameters, microstructure, and phases were investigated. The results showed that when B4C was added, the processing window was enlarged. The minimum energy density was reduced from 457 J/cm2 to 214 J/cm2 when the content of B4C reached 15 wt%. Microstructure orientation was enhanced, and the residual silicon content was decreased from 38 at.% to about 8 at.%. Small pores were turned into large pores with the increase of B4C addition. The findings indicate that the addition of B4C increases the amount of liquid phase during the laser sintering process of silicon carbide, improving the SiC struts' density and reducing the residual silicon by reacting with it. Therefore, the addition of B4C will help improve the application performance of selected laser-sintered silicon carbide under extreme conditions. [ABSTRACT FROM AUTHOR]

Coralline hydroxyapatite (CHA) has been used in clinical for over 20 years. However, coral is an endanger species and has been banned from mining. In addition, coral artificial bone has slow biodegradation of the defects, hindering the growth of new bone. In order to explore the natural coral artificial bone substitute materials, this work proposed using Selective Laser Sintering (SLS) to fabricate natural calcium carbonate/biopolymer composite imitation coral porous structures, and then the surface of the 3D printing product was transformed into a hydroxyapatite thin layer by hydrothermal conversion reaction. The mechanical properties and porosity were optimized by adjusting the SLS processing parameters including laser power, scanning speed and layer thickness. In the composites with the PLLA of 15 wt%, the SLS processing parameters with the laser power of 15 W, laser scanning speed of 1500 mm/s and single layer thickness of 0.08 mm result in the better mechanical properties. After hydrothermal conversion, the products were confirmed to be a mixture of hydroxyapatite (HA) and calcium carbonate by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDX). The TGA results revealed that increasing the reaction temperature or prolonging the reaction time can increase the degree of hydrothermal reaction and thus promote the transformation of calcium carbonate into hydroxyapatite. The results of cytotoxicity assay and Life/Dead staining showed that the scaffold is not toxic to L929 cells. This work has the materials system innovation and focuses on the study of the effects of the SLS and hydrothermal processes on the mechanical performance and the degree of hydroxylation. Then, the preparation process of imitation coral artificial bone preparation was optimized. it is concluded that the imitation coral artificial bone is a nontoxic biomaterial; however, further study on its osteogenic capacity should be warranted in the future. [ABSTRACT FROM AUTHOR]

Silicon Carbide (SiC) ceramic lattice structures were pivotal in advancing space technology and other sectors by merging structural lightness with high strength. This study explored non-uniform lattice designs tailored for specific load-bearing applications to maximize lightness, although machining such SiC structures proved challenging due to their high hardness and wear resistance. Selective Laser Sintering (SLS) was employed to fabricate non-uniform lattice structures featuring graded volume fractions. Micro computed tomography (Miro-CT) characterized the geometric characteristics of the macroscopic non-uniform lattice structure. Extensive investigations were conducted on the impact of these gradient structures on the quasi-static compressive behavior and mechanical properties of SiC ceramics, revealing that the R-A structure achieved a maximum compressive strength of 14.989 MPa and a specific strength of 13.268 × 10³ N·m/kg, approximately double that of a uniform structure. Furthermore, a finite element model (FEM) was established to verify and predict the mechanical and fracture responses of SiC-based structures, showing effective dispersion of stress concentration along the outer rim of the R-A structure, markedly alleviating the usual stress concentration found in traditional lattices and averting catastrophic failure. The alignment between experimental and simulation outcomes substantiated these findings. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, glass fiber (GF)/phenol formaldehyde resin (PF)/epoxy resin (EP) three-phase electrical insulating composites were fabricated by selective laser sintering (SLS) additive manufacturing technology and subsequent infiltration. In the three-phase composites, glass fibers modified by a silane coupling agent (KH-550) were used as reinforcements, phenol formaldehyde resin acted as the binder and matrix, and infiltrated epoxy resin was the filler. Mechanical and electrical properties such as tensile strength, bending strength, dielectric constant, electrical conductivity, and electric breakdown strength of the GF/PF/EP three-phase composite parts were investigated. The results indicated that after being infiltrated with EP, the bending strength and tensile strength of the GF/PF/EP composites increased by 30% and 42.8%, respectively. Moreover, the flexural strength and tensile strength of the GF/PF/EP composite increased with the increase of the glass fiber content. More importantly, the three-phase composites showed high electrical properties. Significant improvement in the dielectric constant, electric breakdown strength, and resistivity with the increase in the content of glass fiber was observed. This enables the prepared GF/PF/EP composites to form complex structural electrical insulation devices by SLS, which expands the materials and applications of additive manufacturing technology. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced silicon carbide (C f /SiC) composite was fabricated by infiltrating liquid silicon (Si) into the carbon preform, which was built by selective laser sintering (SLS) additive manufacturing process from the phenolic resin coated carbon fiber powder with addition of submicron Si. The effect of Si addition on the microstructures of the laser-sintered green part, carbon preform and derived C f /SiC composite was investigated. The results show that the introduced submicron Si plays an important role in reducing porosity and average pore size of the carbon preform, and contributes to improving the microstructure homogeneity of C f /SiC composite by reducing the size of continuous bulk carbon in the preforms. The maximum density, flexural strength and fracture toughness of the C f /SiC composite are 2.89 ± 0.01 g/cm3, 237 ± 9.6 MPa and 3.56 ± 0.24 MPa m1/2, respectively. The coefficient of thermal expansion (CTE) of the C f /SiC composite is approximately 5.5 × 10−6/K from 25 to 900 °C, and the thermal conductivity is in the range of 74–84 W/m·K at room temperature, while decreases to 35–40 W/m·K at 900 °C. • The introduced submicron Si improves the microstructure homogeneity of the C f /SiC composites. • The mechanism of SiC formation is explained in terms of solution and precipitation. • The CTE and thermal conductivity of the C f /SiC composites from RT to 900 °C are evaluated. [ABSTRACT FROM AUTHOR]

Abstract Selective Laser Sintering (SLS) is one of the most mature and engineered polymeric 3D printing technologies, and the produced part is characterized by homogeneous polymorphism, which make the sintered material possess an ordered crystalline phase distribution and thus present a self-formed composite structure. This is due in large part to the special processing method during the SLS process. However, molecular motion mechanism between different phases remain unclear and further exploration is needed. Therefore, this paper firstly investigates the molecular motion mechanism concerning special composite phase structure of SLS-processed PA6 based on 2D correlation fourier transform mid-infrared (FT-MIR) spectra. The results show that although the crystal structure of the LT-α phase is less-ordered, the groups in LT-α change later than those in HT-α as the temperature increases. The overall movement sequence is: HT-α ˃ interphase ˃ LT-α, and the motion mode in the individual phase is the skeleton movement of carbon chains driven by H-bonds whereas the movement of interphase H-bonds is driven by the synergistic effect of the chain in HT-α. Besides, the symmetric methylene (v s (CH 2)) vibrates firstly both for HT-α and LT-α, and then is the stretching vibration of asymmetric methylene (v a s (CH 2)). Graphical abstract Image 104391 Highlights • This paper firstly investigates the composite phase structure of 3D-printed PA6 based on 2D correlation FT-MIR spectra. • The assignments of laser sintered PA6 concerning HT-α, interphase and LT-α were firstly presented. • The H-bonds in the interphase are mainly linked to the carbon skeletal chain of HT-α spherulites rather than LT-α. • The overall movement sequence of molecular chain is: HT-α ˃ interphase ˃ LT-α. • The v s (CH 2) vibrates firstly both for HT-α and LT-α, and then is the stretching vibration of v a s (CH 2). [ABSTRACT FROM AUTHOR]

Abstract Functional graded cellular materials (FGCMs) have attracted increasing attentions for their improved properties when compared to uniform cellular structures. In this work, graded Gyroid cellular structures (GCSs) with varying gradient directions were designed and manufactured via selective laser melting (SLM). As a reference, uniform structures were also manufactured. The surface morphology and mechanical response of these structures under compressive loads were investigated. Results indicate high manufacturability and repeatability of GCSs manufactured by SLM. Optimized density distribution gives these structures novel deformation and mechanical properties. GCSs with density gradient perpendicular to the loading direction exhibit deformation behaviours similar to uniform ones, while GCSs with the gradient parallel to the loading direction exhibit layer-by-layer deformation and collapse behaviour. A novel phenomenon of sub-layer collapses is found in GCSs with gradient parallel to the loading direction. Furthermore, mathematical models were developed to predict and customize the mechanical properties of graded cellular structures by optimizing the relative density of each layer. These significant findings illustrate that graded cellular structures have high application prospect in various industries, particularly given the fact that additive manufacturing has been an enabler of cellular structure fabrication. Graphical abstract Unlabelled Image Highlights • Continuous graded Gyroid cellular structures (GCSs) were fabricated by SLM. • Novel deformation and mechanical properties were gained compared to uniform cellular. • The effect of gradient direction was investigated for GCSs. • Novel sub-layer collapses are founded in GCSs with gradient along building direction. • Mathematical models were developed to calculate Young's modulus and strength of GCSs. [ABSTRACT FROM AUTHOR]

Abstract This work for the first time investigated the effect of laser scan line spacing on the microstructure, phase evolution and nanohardness of Ti-48Al-2Cr-2Nb/RGO (reduced graphene oxide) metal matrix composites (MMCs) fabricated by selective laser melting (SLM). The results show that with increasing the laser scan line spacing from 80 to 140 μm, the average grain size generally decreases from 10.13 to 8.12 μm. The SLM-processed Ti-48Al-2Cr-2Nb/RGO parts are dominated by high-angle (>15°) grain boundaries (HAGBs) and α 2 (Ti 3 Al) phase. With the increase in laser scan line spacing, the contents of HAGBs and α 2 phase both decrease. Due to instantaneous high temperature during the SLM process, some RGO sheets transform to amorphous carbon. The nanohardness of SLM-processed Ti-48Al-2Cr-2Nb/RGO parts increase from 8.13 ± 0.39 GPa to 9.85 ± 0.46 GPa when increasing the laser scan line spacing from 80 to 140 μm, which is much higher than that of the traditional casting TiAl counterparts (4.98 ± 0.10 GPa). Graphical Abstract Unlabelled Image Highlights • The average grain size generally refines with increasing the laser scan line spacing. • The phase transformation mechanism during SLM is determined by HRTEM. • Some RGO sheets transform into amorphous carbon during SLM process. • The nanohardness is much higher than those casting counterparts. [ABSTRACT FROM AUTHOR]

Polyamide 6 (PA6) have been extensively employed in manufacturing engineering plastic alternatives to metal in automotive field owing to their high specific strength, good damping and thermal properties. However, the selective laser sintering (SLS) availability of high performance PA6 is not thoroughly investigated. This paper firstly investigates the processability, recyclability and crystalline structure of SLS PA6 powder in comparison with the widely used Polyamide 12 (PA12). The results show that the PA6 powder has a relatively sphere shape, an appropriate average particle size 58.9 μm, a wide sintering window up to 36.73 °C (c. 6 °C wider than PA12) and similar crystallinity 47.61% comparable to PA12, indicating an excellent SLS processability. However, the used PA6 powder shows a directly fragmenting behavior, a substantially narrowed sintering window (decreased by 13.15 °C) and a dramatically declined crystallinity (down to 21.8%), indicating a relatively inferior recyclability compared with PA12. The sub-T pm1 crystallization transition concerning α phase was found for SLS PA6 part, which is derived from the release of strain energy absorbed during SLS processing and has advantageous effects on part ductility. This work confirms that it is available and promising for the application of high performance PA6 in SLS. [ABSTRACT FROM AUTHOR]

The microstructures and compressive properties of Ti-46.5Al-2.5Cr-2Nb-0.5Y alloy with varied boron (B) addition processed by selective laser melting (SLM) had been systematic studied. With increasing the B content from 0 to 2 wt%, the average grain size of SLM-processed Ti-46.5Al-2.5Cr-2Nb-0.5Y/B composites decreased from 16.64 µm to 5.66 µm, meanwhile, the {0001} texture index and high angle grain boundaries (HAGBs) increased from 10.78 and 87.9% to 22.69 and 94.4%. The phase evolution mechanism of Ti-46.5Al-2.5Cr-2Nb-0.5Y/B composites during the SLM process can be summarized as: firstly, β and B phases precipitated out from the liquid phase, then the β phase transformed to α phase and part of the α phase transferred to γ phase, later, some new phases of TiB 2 and AlB 2 emerged by the diffusion mechanism of B, Ti and Al atoms, and then the β and α phases orderly transformed to B 2 and α 2 , lastly, the γ, B 2 , B, TiB 2 , AlB 2 phases in a range of several hundred nanometers were randomly distributed within the α 2 matrix. Due to the grain refinement strengthening mechanism, the compressive strength and strain of Ti-46.5Al-2.5Cr-2Nb-0.5Y/B parts increased to the maximum of 1610.53 MPa and 5.17%. [ABSTRACT FROM AUTHOR]

Ti-Nb alloys were in-situ fabricated by selective laser melting (SLM) to study the effect of Nb content on their phase transformation, microstructure evolution, mechanical properties and in vitro apatite-forming capability. Results show that α' martensite and β (Ti, Nb) phase are obtained in SLM-processed Ti-Nb alloys. The increase of Nb content results in the increase of β phase amount but decrease of β grain dimension. The former effect is due to the suppression of martensitic transformation and strengthening of solid solution behavior, while the latter phenomenon can be attributed to the increase of heterogeneous nucleation sites. The Ti-25Nb alloy possesses the lowest modulus of 18.7 ± 1.4 GPa due to the maximum content of β phase. The SLM-processed Ti-45Nb alloy exhibits superior strength of 1030 ± 40 MPa and microhardness of 356 ± 7 HV 0.1 , which is 97.32% and 52.53% higher than cast ones, respectively. The in vitro apatite-forming capability of Ti-25Nb alloy is the most superior compared to other Ti-Nb alloys. It demonstrates that β phase has the ability to induce apatite formation. The research shows that SLM could be used for in-situ fabrication of Ti-Nb bone implants with tailored mechanical and biomedical properties by adjusting Nb addition. [ABSTRACT FROM AUTHOR]

The crystallographic texture, phase composition and evolution, and nanohardness of a Ti–45Al–2Cr–5Nb alloy processed by selective laser melting (SLM) at various substrate preheating temperatures were investigated. The α 2 phase decreases whereas the γ and B 2 phases increase with increasing preheating temperature, and the relationship in orientation between B 2 , α 2 and γ phases is described as follows: 11 2 ̅ 0 α 2 / / 111 γ / / 111 B 2 . The SLM-processed TiAl alloy shows much higher nanohardness than its traditional casting counterpart, which increases with the increase of preheating temperature. The findings would be a valuable reference for fabricating TiAl components with acceptable texture, phase compositions and nanohardness by SLM. [ABSTRACT FROM AUTHOR]

Novel binder-coated Al 2 O 3 sands were prepared for selective laser sintering (SLS) to manufacture complex sand moulds for metal casting. The solidification mechanisms of the coated sands during the SLS and post-curing processes were provided, and effects of binder content, raw sand type and post-curing parameters on the strength and gas evolution were investigated. At the same binder content, the strength of the Al 2 O 3 sand SLS specimen is much higher than that of commonly used quartz sand. Therefore, the binder-coated Al 2 O 3 sands are very suitable for building large sand moulds with thin walls and delicate structures. On the other hand, to meet the same strength requirement for metal casting process, the Al 2 O 3 sands need less binder content, consequently reducing gas evolution and thus improving the quality of final castings. Finally, a large sand mould for casting a complex six-cylinder diesel engine cylinder head was successfully manufactured by the SLS of the binder-coated Al 2 O 3 sands, and the final casting with the surface quality and dimensional accuracy meeting the specific design requirements was obtained. The materials and method proposed in this paper not only shortened the trial production cycle of the six-cylinder engine from five months of the traditional casting method to 10 days, but also reduced the cost and improved the casting quality. [ABSTRACT FROM AUTHOR]