As a non-beam-based additive manufacturing (AM) method, binder jet 3D printing (BJ3DP) is a process in which a liquid binder is jetted on layers of powdered materials, selectively joined, and then ...followed by densification process. Among AM technologies, binder jetting holds distinctive promise because of the possibility of rapid production of complex structures to achieve isotropic properties in the 3D printed samples. By taking advantage of traditional powder metallurgy, BJ3DP machines can produce prototypes in which material properties and surface finish are similar to those attained with traditional powder metallurgy. Various powdered materials have been 3D printed, but a typical challenge during BJ3DP is developing printing and post-processing methods that maximize part performance. Therefore, a detailed review of the physical processes during 3D printing and the fundamental science of densification after sintering and post–heat treatment steps are provided to understand the microstructural evolution and properties of binder jetted parts. Furthermore, to determine the effects of the binder jetting process on metallurgical properties, the role of powder characteristics (e.g., morphology, mean size, distribution), printing process parameters (e.g., layer thickness, print orientation, binder saturation, print speed, drying time), sintering (e.g., temperature, holding time), and post-processing are discussed. With the development of AM technologies and the need for post-processing in 3D printed parts, understanding the microstructural evolution during densification is necessary and here, processing steps are explained. Finally, opportunities for future advancement are addressed.
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•The MAX phase Ti2SnC enhances iron-based self-lubricant composites mechanical properties.•Ti2SnC addition improves mechanical strength but reduces ultimate compressive ...strength.•Graphite addition synergizes with Ti2SnC, lowering the friction coefficient and wear rate.
This work focuses on developing novel iron-based self-lubricating composites reinforced with Ti2SnC MAX phase produced by powder metallurgy. Two amounts of Ti2SnC (5 and 10 vol%) and the addition of 10 vol% graphite were evaluated. The microstructure revealed a partial reaction between the matrix and the Ti2SnC, exhibiting a degree of dissociation in the presence of graphite, leading to the precipitation of carbides. The addition of the MAX phase significantly improved the hardness and compression strength. The dry coefficient of friction was around 0.12 for Fe + 5Ti2SnC + 10Gr, showing a remarkable reduction in wear rate up to 85 % compared to pure iron. The results demonstrate a synergistic effect between the MAX phase and graphite, enhancing tribological performance and wear resistance.
Abstract
Powder metallurgy process can produce excellent quality magnetic targets, in which powder quality affects the quality of the target to a large extent, the production of high-quality target ...has an important role. This paper mainly introduces the preparation methods of powder for targets, summarizes the preparation methods of fine powder and the characteristics of different preparation methods. Finally, it summarizes the shortcomings of the current research on powder for targets, proposes new research ideas, and prospects its future development.
Manufacturing businesses aiming to deliver their new customised products more quickly and gain more consumer markets for their products will increasingly employ selective laser sintering/melting ...(SLS/SLM) for fabricating high quality, low cost, repeatable, and reliable aluminium alloy powdered parts for automotive, aerospace, and aircraft applications. However, aluminium powder is known to be uniquely bedevilled with the tenacious surface oxide film which is difficult to avoid during SLS/SLM processing. The tenacity of the surface oxide film inhibits metallurgical bonding across the layers during SLS/SLM processing and this consequently leads to initiation of spheroidisation by Marangoni convection. Due to the paucity of publications on SLS/SLM processing of aluminium alloy powders, we review the current state of research and progress from different perspectives of the SLS/SLM, powder metallurgy (P/M) sintering, and pulsed electric current sintering (PECS) of ferrous, non-ferrous alloys, and composite powders as well as laser welding of aluminium alloys in order to provide a basis for follow-on-research that leads to the development of high productivity, SLS/SLM processing of aluminium alloy powders. Moreover, both P/M sintering and PECS of aluminium alloys are evaluated and related to the SLS process with a view to gaining useful insights especially in the aspects of liquid phase sintering (LPS) of aluminium alloys; application of LPS to SLS process; alloying effect in disrupting the surface oxide film of aluminium alloys; and designing of aluminium alloy suitable for the SLS/SLM process. Thereafter, SLS/SLM parameters, powder properties, and different types of lasers with their effects on the processing and densification of aluminium alloys are considered. The microstructure and metallurgical defects associated with SLS/SLM processed parts are also elucidated by highlighting the mechanism of their formation, the main influencing factors, and the remedial measures. Mechanical properties such as hardness, tensile, and fatigue strength of SLS/SLM processed parts are reported. The final part of this paper summarises findings from this review and outlines the trend for future research in the SLS/SLM processing of aluminium alloy powders.
Due to the high specific strength of titanium, materials on its base are contemplated as a viable alternative in low-weight armor production. However, when the armor parts are fabricated using ...traditional and costly ingot and wrought technology, the feasibility of implementation is questionable. Proposed cost-efficient process of fabrication uses blended elemental powder metallurgy (BEPM). Multi-layered structures based on Ti-6Al-4 V alloy and its metal-matrix composites (MMC) with 5–10% (vol.) of TiC and TiB were fabricated and tested. Relatively large multi-layered plates and bars with TiC composite were successfully sintered due to very close shrinkage values of the alloy and composite. Shrinkage values of TiB composites were substantially lower than those for alloy, what led to delamination of layered structures, cracking and distortion of the plates. The difference in shrinkage behavior between the ML plates with TiC vs. TiB MMCs was explained by the difference in the ways those two types of reinforcement particles evolve within the structures. We have shown that by the optimization of the powder size and hydrogen content in BEPM process the shrinkage mismatch of the layered structures could be effectively nullified.
For conventional titanium matrix composites (TiMCs), there is always a trade-off issue between enhanced strength and ductility of these materials. In this study, we explore a new design methodology ...by reinforcing titanium alloy matrix with carbonaceous nanomaterials and investigate the mechanisms for achieving a good balance of their strength and ductility. The TiMCs were synthesized through a low-cost powder metallurgy route using pre-mixed Ti-6Al-4V (TC4) powders and various carbon based nanofillers, including graphite powders (GPs), graphene oxide nanosheets (GONs) and graphene nanoplates (GNPs), and were further rolled at a temperature of 1173 K with a deformation of 66.7%. Among these three types of carbon reinforcing sources, the GNPs are more easily reacted with TC4 matrix and form more contents of TiC phases after sintering owing to their larger amounts of defects than those of the GPs and GONs. TiC products are identified to play a bridging role for not only connecting the TC4 matrix but also forming coherent interfaces with the TC4 matrix, thus facilitating a strong interfacial bonding of the composites. The as-rolled GNPs/TC4 composites exhibit a 0.2% yield strength of 1146.36 MPa (with an elongation of ∼8.1%), which is 24.6%, 9.22% and 5.62% higher than those of pure TC4, GPs/TC4 and GONs/TC4 composites. The GNPs/TC4 nanocomposites show a better balance of strength and ductility than those of the other two types of nanocomposites. The synergetic strengthening mechanisms are identified to be Orowan strengthening effect, effective load transfer capability of GNPs, and in-situ formation of interfacial TiC structures, which provide optimum interfacial microstructures to achieve good mechanical properties of the TiMCs.
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This study aims to investigate the role of graphene on wear and corrosion behaviors of pure magnesium. Magnesium/Graphene Nanoparticle (GNP) composites were fabricated via semi powder metallurgy ...method with a different content of graphene (0.1, 0.25 and 0.5 wt%). The effect of graphene in pure magnesium was examined by hardness, wear and corrosion tests. Microstructural and phase analysis were carried out by Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis. Experimental results revealed that, hardness values increased with the addition of graphene. There was a same trend in wear behaviors with increase of graphene rate. The best wear performance was belonging to the 0.50 wt% graphene/mg composite under load of 10N. So improvement of wear properties was achieved using graphene as reinforcement. According to the microstructural evolution, the uniform distribution was achieved for all samples but partially agglomeration could be seen in Mg-0.50 wt% graphene. Compared to the pure magnesium, corrosion performance was affected negatively in graphene reinforced composites.
•Graphene reinforced was used as a reinforcement with different content (0.1,0.25,0.5 wt%) for magnesium matrix composite.•Composites were produced by semi powder metallurgy method that is based on solution.•Mechanical properties of pure magnesium were improved with the addition of graphene.•Wear resistance was enhanced directly with graphene content.•Graphene has negative effect for corrosion performance of magnesium.
In this study, Cu-based nanocomposites using nanographite, graphene nanosheet and carbon nanotubes have been fabricated by flake powder metallurgy. The objective of using different reinforcement ...contents is to assess their effect on the microstructure, density, electrical conductivity and hardness of Cu-based nanocomposites. The results show that the average particle size of the prepared Cu-based nanocomposite powders with reinforced 5 wt.% nanographite, graphene nanosheet and Cu-CNT nanocomposite are 97.8, 94.9 and 49.7 μm, respectively. The lowest final density 6.73 g/cm3 for sintered Cu-5 wt.% CNT nanocomposites, while the highest density value was 8.78 g/cm3 for sintered Cu-0.5 wt.% nanografit nanocomposites. For all nanocomposite groups, increasing the reinforcement content from 0.5 to 5 wt.% results in an decrease in hardness values. The electrical conductivity of the Cu-0.5 wt.% graphene nanosheet was approximately 79 IACs, and this value decreased slightly to 62 IACs with increasing graphene nanosheet content.
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•Cu-based nanocomposites were successfully fabricated by flake powder metallurgy.•Microstructure, density, electrical conductivity and hardness of the samples were studied.•The effects of content and ratio of reinforcement was investigated.
The preparation and properties of reduced graphene oxide (rGO) and graphene nanosheets (GNSs) reinforcement of aluminium matrix nanocomposites (AMCs) are reported. For the rGO-AMCs, commercial ...colloidal GO was coated onto aluminium powder particles and then reduced via thermal annealing. For the GNS-AMCs, graphene exfoliated from graphite through ultrasonication and centrifugation was coated onto aluminium particle surfaces via dispersion mixing, filtering and drying. Pure aluminium and aluminium composites with various reinforcement concentrations of rGO and GNS were cold compacted into disc-shaped specimens and sintered in inert atmosphere. The mechanical properties and microstructure were studied and characterised via Vickers hardness, X-ray diffraction, density measurement, and scanning electron microscopy. The reinforcements were uniformly distributed onto the aluminium particle surfaces before and after consolidation within the composites. The relevant factors for the powder metallurgy process (compaction pressure, density, and sintering conditions) were optimised. Increased levels of increased hardness were recorded, over baseline compacted and sintered pure aluminium samples, prepared under identical experimental conditions, of 32% and 43% respectively for the 0.3wt.% rGO-Al and 0.15wt.% GNSs-Al composites. The process developed and presented herein provides encouraging results for realising rGO-AMC and GNS–AMC nanocomposites via low cost cold powder compaction and sintering metallurgy techniques.
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•Developed powder metallurgy method for rGO and GNS-aluminium matrix composites•Mechanical and chemical property determination of for graphene–aluminium composites•Significant increase in composite compact hardness over pure metal baseline•Correlation of composite density with compaction pressure and reinforcement levels•Elaboration of areas of focus on method for further improvements in graphene-AMCs
A flake powder metallurgy route consists of a slurry based dispersion process and a short time ball milling process was proposed to fabricate strong and ductile CNT/Al composites reinforced with high ...content CNTs. To improve the interfacial bonding, the CNT/Al nanoflake powders prepared through slurry based dispersion process would go through a short time high energy ball milling process to break native Al2O3 skin and embed CNTs into Al matrix. With the dispersion homogeneity and well-maintained structural integrity of CNTs achieved by the slurry based dispersion, and improvement of interfacial bonding from non-bonding to physical bonding/diffusion assisted bonding and partial reaction bonding through the short time ball milling, an enhancement of tensile strength from 298 to 406 MPa and ductility from 1.9 to 8.8% was obtained for the 2 h ball-milled 3 vol.% CNT/Al composites, compared to the composites fabricated by sole slurry based dispersion process. It also outperformed that fabricated by direct high energy ball milling, indicating the flake powder metallurgy method could provide a good coordination between the CNT dispersion homogeneity, structural integrity and interfacial bonding.
Comparison of the mechanical properties and microstructure of 3 vol.% CNT/Al fabricated by slurry dispersion process (blue frame) and by slurry dispersion plus 2 h ball milling process (red frame). Display omitted
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