Search Results (23)

The brittleness of 18-karat purple gold originates from the AuAl₂ intermetallic compound. This study investigates the microstructural modification of the AuAl₂ intermetallic compound by adding silicon (Si) and cobalt (Co) and by rapid solidification in copper molds. The samples with alloy additions from a traditional investment casting were compared with copper mold casting for grain boundary characteristics using SEM, EBSD, and TEM. SEM micrographs showed a reduction in grain size of copper mold casting from approximately within 150–200 μm to within 12–20 μm. EBSD showed a narrow grain size distribution in the Si–Co-modified alloy than in the Si-modified alloy, using the copper mold casting technique. TEM observations show that grain boundaries were closely packed, with ~80 nm-sized voids. XRD confirmed that all alloys retained the AuAl₂ intermetallic phase, with peak broadening in the modified and fast-cooling samples indicating crystallographic refinement. These results confirm that Si-Co additions with a fast cooling rate effectively refine the microstructure of the AuAl₂ intermetallic compound, making the alloy less brittle while preserving the purple gold color. Full article

In precision manufacturing, selecting the most economically viable process is essential for low-volume, high-complexity applications. This study compares the machining process (MP), conventional investment casting (CIC), and rapid prototyping (RP) through a mathematical cost model based on the activity-based costing (ABC) approach. The model captures detailed cost drivers across design, logistics, production, and environmental dimensions. Results show that MP incurs the highest production cost (94.45%) but minimal logistics (3.43%). CIC bears the highest total cost and significant production overhead (93.2%), while RIC achieves the lowest total cost, driven by major savings in production (84.6%) and labor. Although RIC has slightly higher logistics than MP, it demonstrates superior economic efficiency for small-batch, high-accuracy production. This study provides a unified quantitative framework for cost comparison and offers valuable guidance for manufacturers aiming to enhance efficiency, sustainability, and profitability across diverse fabrication strategies. Full article

Considering the importance of the automotive industry, reducing the environmental impact of automotive component manufacturing is crucial. Additionally, lightening of the latter promotes a reduction in fuel consumption throughout the vehicle’s life cycle, limiting emissions. This study presents a comprehensive approach to optimizing and manufacturing a MacPherson steering knuckle using topology optimization (TO), additive manufacturing, and rapid investment casting (RIC). Static structural simulations confirmed the mechanical integrity of the optimized design, with stress and strain values remaining within the elastic limits of the SG A536 iron alloy. The TO process achieved a 30% reduction in mass, resulting in lower material use and production costs. Additive manufacturing of optimized geometry reduced resin consumption by 27% and printing time by 9%. RIC simulations validated efficient mold filling and solidification, with porosity confined to removable riser regions. Life cycle assessment (LCA) demonstrated a 27% reduction in manufacturing environmental impact and a 31% decrease throughout the component life cycle, largely due to vehicle lightweighting. The findings highlight the potential of integrated TO and advanced manufacturing techniques to produce structurally efficient and environmentally sustainable automotive components. This workflow offers promising implications for broader industrial applications that aim to balance mechanical performance with ecological responsibility. Full article

Investment casting is a precision casting technology that can produce complex shapes from various materials, particularly difficult-to-cast and difficult-to-machine metallic alloys. Meanwhile, electrical discharge machining (EDM) is a well-known technique for producing ultra-precise mechanical parts, and electrode quality is crucial. Few studies have explored how rapid prototyping (RP) pattern generation and investment casting influence the final product’s shape, dimensions, and surface roughness. This study investigates EDM electrode fabrication using investment casting and RP-generated epoxy resin patterns. We examine the effects of electrode materials (CuZn5, CuZn30, and FeCr24) on surface roughness, alongside the impact of ceramic shell thickness and RP pattern shrinkage on electrode quality. The EDM electrodes have a shrinkage of 0.8–1.9% and a surface roughness of 3.20–6.35 μm, depending on the material selections. Additionally, the probability of shell cracking decreases with increasing shell thickness, achieving stability at 16.00 mm. This research also applies investment casting electrodes to process DC53 steel. The results indicate that the surface roughness of the workpiece after EDM machining with different electrode materials is in the range of 4.71 µm to 9.88 µm. The result expands the use of investment casting in electrode fabrication, enabling the production of high-precision electrodes with complex profiles and challenging materials, potentially reducing both time and cost. Full article

In the domain of metal casting, investment casting is recognized for its proficiency in producing high-quality castings. This method involves the utilization of a melt out, burnout, or soluble patterns to create ceramic molds. The present investigation explored the potential of utilizing fused deposition modeling (FDM) patterns fabricated from polyvinyl alcohol (PVA). An examination of the structural characteristics and properties of several commercially available PVA filaments, along with an evaluation of the as-printed samples, were provided in this study. It was demonstrated that commercial PVA filaments may contain additives that can lead to elevated ash content following pattern burnout and reduced strength in as-printed samples. Experiments on PVA dissolution in water revealed that, for high dissolution rates of the pattern, not only high temperature, but also water medium mixing was necessary. The colloidal silica binder, a common component in ceramic mold manufacturing, exhibited effective wetting properties of the patterns, while generally preventing significant dissolution, which can adversely impact pattern quality. The PVA filaments under investigation were utilized to fabricate patterns for the impeller cast parts. Subsequent to this, ceramic molds were obtained, and castings made of nickel superalloy were produced. The investigation revealed that the Bambu Lab filament, which is PVA without additives, exhibited the lowest defect rate in both the mold and the casting. In summary, this study demonstrates that the 3D printing of investment casting patterns holds considerable promise as a rapid casting technique. Full article

The rapid investment casting (RIC) process requires a 3D-printed pattern to create a ceramic mold. Stereolithography (SLA) is a commonly used 3D printing method for pattern creation due to its ability to print complex shapes with smooth surfaces. The printing parameters can significantly affect the dimensional accuracy of the pattern. This study examines how different build orientations (0°, 45°, and 90°) affect the dimensional accuracy of parts produced using SLA. The specimens were printed using castable wax resin. They were measured to investigate the dimensional deviations using 3D scanning technology to understand the correlation between orientation and accuracy better. It was found that the orientation of the print affects the overall accuracy significantly. Parts printed at a 45° angle generally showed the smallest deviations from their nominal dimensions, except for certain features. For instance, cylindrical features showed deviations improving from −7.28% at 0° to −4.81% at 90°, while spherical features had deviations decreasing from −5.01% at 0° to −2.46% at 90°. Simple features, such as holes, exhibited minimal deviation across orientations, with the smallest error observed at 45° (1.98%). These results demonstrate different features and build orientations can affect the accuracy of the printed part differently. To ensure better accuracy, parts printed in different build orientations will require varying amounts of compensation during the design stage. By managing build orientations and controlling the inherent limitations of SLA, users can improve the print’s accuracy and meet quality standards more effectively. Research results can help industries optimize print settings and reduce dimensional errors. Full article

Residual stresses and anisotropic structures characterize laser powder bed fusion (L-PBF) products due to rapid thermal changes during fabrication, potentially leading to microcracking and lower strength. Post-heat treatments are crucial for enhancing mechanical properties. Numerous dental technology laboratories worldwide are adopting the new technologies but must invest considerable time and resources to refine them for specific requirements. Our research can assist researchers in identifying thermal processes that enhance the mechanical properties of dental Co-Cr alloys. In this study, high cooling rates (quenching) and annealing after quenching were evaluated for L-PBF Co-Cr dental alloys. Cast samples (standard manufacturing method) were tested as a second reference material. Tensile strength, Vickers hardness, microstructure characterization, and phase identification were performed. Significant differences were found among the L-PBF groups and the cast samples. The lowest tensile strength (707 MPa) and hardness (345 HV) were observed for cast Starbond COS. The highest mechanical properties (1389 MPa, 535 HV) were observed for the samples subjected to the water quenching and reheating methods. XRD analysis revealed that the face-centered cubic (FCC) and hexagonal close-packed (HCP) phases are influenced by the composition and heat treatment. Annealing after quenching improved the microstructure homogeneity and increased the HCP content. L-PBF techniques yielded superior mechanical properties compared to traditional casting methods, offering efficiency and precision. Future research should focus on fatigue properties. Full article

This paper presents a comprehensive analysis of the utilization of 3D printing technology for the fabrication of ceramic shells in the context of investment casting. This study encompasses an exploration of various 3D printing techniques such as binder jetting technology and lithography-based ceramic manufacturing applied to ceramic materials tailored for investment casting applications for different materials. Comparative analyses between conventionally manufactured shells and those produced through 3D printing techniques are presented, shedding light on the potential advantages and challenges associated with the adoption of additive manufacturing in investment casting processes. The findings of this study reveal that both methods offer viable solutions for creating ceramic materials suitable as shells for investment casting. Both lithography-based ceramic manufacturing and binder jetting technology exhibit unique advantages and challenges. Lithography-based ceramic manufacturing demonstrates a superior surface finish and resolution, making it particularly suitable for intricate designs and fine details. On the other hand, binder jetting technology presents advantages in terms of speed and scalability, allowing for the rapid production of larger components. Full article

Shape memory alloy (SMA) bidimensional cellular structures (CSs) have a great potential application in attenuation of vibrations due to reversible martensitic phase transformations induced by thermal or mechanical loading. This work aims to produce a thermal and mechanical characterization of CuAlMn SMA CSs produced by rapid investment casting (RIC). Structures with different unit cell geometries and thicknesses of 0.5 mm and 1 mm were manufactured by centrifugal RIC. Compression tests at different temperatures were performed on the CS to verify its thermomechanical behavior. We observed that a CS with a thickness of 0.5 mm presents greater mechanical strength and lower levels of maximum force at the end of each 5% compression cycle, ranging from approximately 1/10 to 1/3, compared to structures with a thickness of 1 mm. Among all the CS configurations, the re-entrant structure exhibited higher levels of force, with higher secant stiffness and dissipated energy. The structures resisted the application of compressive forces that varied between 125 N and 500 N for the 0.5 mm CS and between 500 N and 5500 N for the 1 mm CS. Therefore, the results showed that all CuAlMn SMA CSs produced by RIC exhibited sufficient strength to attain strain levels of up to 5% at different temperatures, and that the unit cell geometry can be used to tune the mechanical properties. Full article

With increasing interest in the rapid development of lattice structures, hybrid additive manufacturing (HAM) technology has become a competent alternative to traditional solutions such as water jet cutting and investment casting. Herein, a HAM technology that combines vat photopolymerization (VPP) and electroless/electroplating processes is developed for the fabrication of multifunctional polymer-metal lattice composites. A VPP 3D printing process is used to deliver complex lattice frameworks, and afterward, electroless plating is employed to deposit a thin layer of nickel-phosphorus (Ni-P) conductive seed layer. With the subsequent electroplating process, the thickness of the copper layer can reach 40 μm within 1 h and the resistivity is around $1.9\times {10}^{-8} \mathsf{\Omega }\cdot \mathrm{m}$, which is quite close to pure copper ($1.7 \times {10}^{-8} \mathsf{\Omega }\cdot \mathrm{m}$). The thick metal shell can largely enhance the mechanical performance of lattice structures, including structural strength, ductility, and stiffness, and meanwhile provide current supply capability for electrical applications. With this technology, the frame arms of unmanned aerial vehicles (UAV) are developed to demonstrate the application potential of this HAM technology for fabricating multifunctional polymer-metal lattice composites. Full article

Rapid investment casting is a casting process in which the sacrificial patterns are fabricated using additive manufacturing techniques, making the creation of advanced designs possible. One of the popular 3D printing methods applied in rapid investment casting is stereolithography because of its high dimensional precision and surface quality. Printing parameters of the used additive manufacturing method can influence the surface quality and accuracy of the rapid investment cast geometries. Hence, this study aims to investigate the effect of stereolithography printing parameters on the dimensional accuracy and surface roughness of printed patterns and investment cast parts. Castable wax material was used to print the sacrificial patterns for casting. A small-scale prosthetic biomedical implant for total hip replacement was selected to be the benchmark model due to its practical significance. The main results indicate that the most significant stereolithography printing parameter affecting surface roughness is build angle, followed by layer thickness. The optimum parameters that minimize the surface roughness are 0.025 mm layer thickness, 0° build angle, 1.0 support density index, and across the front base orientation. As for the dimensional accuracy, the optimum stereolithography parameters are 0.025 mm layer thickness, 30° build angle, 0.6 support density index, and diagonal to the front base orientation. The optimal printing parameters to obtain superior dimensional accuracy of the cast parts are 0.05 mm layer thickness, 45° build angle, 0.8 support density index, and diagonal to the front model base orientation. With respect to the surface roughness, lower values were obtained at 0.025 mm layer thickness, 0° build angle, 1.0 support density index, and parallel to the front base orientation. Full article

Aiming at the problems of the complex shape, difficult three-dimensional (3D) digital modeling and high manufacturing quality requirements of gas turbine blades (GTB), a method of fitting the blade profile line based on a cubic uniform B-spline interpolation function was proposed. Firstly, surface modeling technology was used to complete the fitting of the blade profile of the GTB, and the 3D model of the GTB was synthesized. Secondly, the processing parameters of the additive manufacturing were set, and the GTB model was printed by fused deposition technology. Then, the rapid investment casting was completed with the printed model as a wax model to obtain the GTB casting. Finally, the blade casting was post-processed and measured, and it was found to meet the requirements of machining accuracy and surface quality. Full article

With the aid of virtual prototyping and casting numerical simulation, this work presents the optimization of an injection system used in a non-traditional investment casting process that applies perpendicular centrifugal force to inject the molten metal into refractory plaster molds. In this study, advanced techniques of simulation and production of complex geometries in Computer-Aided Design CAD (Computer-Aided Design) are used in the design of the casting system of a miniaturized simple-cubic cell structure. The cast part has a complex shape profile and needs a high surface finish with strict dimensional tolerance. The alloy used to fill the mold is an aluminum bronze shape memory alloy (SMA). CAD was used to model the part and the proposed models for casting optimization. ProCAST software was used for the numerical simulation of the casting process. Experimental parameters were used as input data for the numerical simulation. The simulation results were analyzed focusing on the identification of defects in the Cu–Al–Mn SMA simple-cubic structures. Different feeding systems have been designed to eliminate the identified defects. Concerning the molten recirculation, the optimal nozzle model has a truncated cone profile, with a larger radius of 6.5 mm, a smaller radius of 2.0 mm and a height of 8.0 mm (called here model 3). Experimental observations from cast SMA parts agree with the simulated results of the optimized nozzle model 3. In addition to the elimination of alloy recirculation with the nozzle optimization in this work, the shrinkage porosity at the upper base of the part was eliminated with the addition of a compensation volume close to the region where porosity is more intense. By exploring the possibilities offered by commercial software, the work contributes to advance the knowledge and application of the non-traditional investment casting process, highlighting its advantages and potential applications. Full article

Porous structures of magnesium alloys are promising bioimplants due to their biocompatibility and biodegradability. However, their degradation is too rapid compared to tissue regeneration and does not allow a progressive metal substitution with the new biological tissue. Moreover, rapid degradation is connected to an accelerated ion release, hydrogen development, and pH increase, which are often causes of tissue inflammation. In the present research, a natural organic coating based on tannic acid was obtained on Mg AZ91 porous structures without toxic reagents. Mg AZ91 porous structures have been prepared by the innovative combination of 3D printing and investment casting, allowing fully customized objects to be produced. Bare and coated samples were characterized using scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), fluorescence microscopy, Fourier transformed infrared spectroscopy (FTIR), tape adhesion test, Folin–Ciocalteu, and degradation tests. Different parameters (solvent, dipping time) were compared to optimize the coating process. The optimized coating was uniform on the outer and inner surfaces of the porous structures and significantly reduced the material degradation rate and pH increase in physiological conditions (phosphate-buffered saline—PBS). Full article

The rapid rise of China on the global stage has promoted a widely held concern about the country’s political intention behind its expanding overseas economic activities. This paper attempts to shed new light on this old question: Is the abundance of natural resources in Africa the primary motivation for Chinese economic engagement in the continent? To this end, we investigate the nexus of China’s direct investment in 54 African countries and its international trade with the region between 2003 and 2014 to estimate how and to which extent Chinese investment affects its trade with the continent. This empirical task is facilitated using a transaction-level trade database from Chinese customs, which allows us to trace the trade records by product, destination, and exporting firm. Our empirical results support the trade-promoting effect of China’s foreign direct investment in the region, and this effect is found to be more significant for China’s exports of consumption and processed goods to the continent than for China’s imports of primary goods from this same region. Furthermore, we do not find systematic evidence that these investment activities lead to more primary goods being imported by Chinese state-owned enterprises. While these findings do not rule out the existence of resource-seeking motivation, they cast doubt on that being a primary driving force behind Chinese investment in Africa. Full article