In the present study, aluminium metal matrix composites (AMCs) were successfully produced through stir-squeeze casting using a novel approach. The feasibility of using car scrap aluminium alloy ...wheels (SAAWs) as the matrix material and spent alumina catalyst (SAC) from oil refineries as reinforcement material was investigated. For the purpose of comparision, composites were also produced using AlSi7Mg (LM25 grade) aluminium alloy as a matrix and alumina as reinforcement particles through the stir-squeeze casting process. In total, four different combinations of composites (AlSi7Mg + alumina; scrap aluminium alloy + alumina; AlSi7Mg + spent alumina catalyst; scrap aluminium alloy + spent alumina catalyst) were produced and characterized. Microstructural investigations using an optical microscope and a scanning electron microscope (SEM) as well as energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) revealed that in all four composites the reinforcement formed a mixture in the eutectic silicon phase of the matrix alloy. The alumina particles' size and content ratio greatly influenced this mixture's formation and morphology. The composites produced using alumina exhibited smaller pore sizes and lower porosity as compared to the composites produced with a spent alumina catalyst. Superior mechanical properties were also obtained when using alumina as reinforcement, and better mechanical properties can mainly be attributed to the morphology of the reinforcement and silicon eutectic phase mixture. The scrap aluminium alloy + alumina exhibited the lowest porosity (7.3%) and abrasive wear loss (0.11 mg for the finest abrasive), highest hardness (58.5 BHN), and second highest ultimate tensile strength (UTS) (125 MPa) and ultimate compressive strength (UCS) (312 MPa) among the four composites.
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•A novel approach used to produce metal matrix composites from waste materials.•The alumina reinforcement combines with the eutectic silicon to form a mixture.•Acicular, blunted, needle-like mixture morphology improves mechanical properties.•Enhanced ultimate tensile (125 MPa) and compressive strength (312 MPa) obtained.
Study on direct laser metal deposition Ghosal, Puja; Majumder, Manik Chandra; Chattopadhyay, Anangamohan
Materials today : proceedings,
2018, 2018-00-00, Volume:
5, Issue:
5
Journal Article
Peer reviewed
In the current economic situation with worldwide trend for developing new products, the importance of time and cost reduction increases day-by-day. To achieve this goal the man-machine-material ...interaction should be maximized. Direct laser metal deposition (DLMD) is one of the most famous approaches for this. DLMD is one kind of 3D printing technology (Additive Manufacturing) together with laser cladding process. In DLMD, it is possible to fabricate fully functional metallic parts directly from CAD data, which involves a feeding of metal powders through a nozzle into a high power laser beam and creates a melt pool on the surface of the solid substrate upon which a metallic powder is injected. DLMD process are now acknowledged worldwide and is also known to all by several other names such as Laser metal deposition (LMD), Direct laser deposition (DLD), Laser engineered net shaping (LENS), Direct light fabrication (DLF), Laser deposition welding (LDW) and powder fusion welding (PFW). The role of nozzle in this process is as important as the heart of a human being. There are verity of nozzle configurations namely off-axis, continuous coaxial and discontinuous coaxial powder injection. Comparison of these types towards specific applications revels very interesting observations which are subsequently reproduced in this article. In DLMD, laser beam and powder metals are fed through the nozzle onto a metallic substrate. Then, powder melts by the laser heat and creates a metal pool on the solid substrate by fusion bonding. Once the feedback control sensor gives feedback of completion of deposition of a layer, the laser head, along with the powder delivery nozzle, move up. The whole process is carried out until final near-net-shape of the metal part or component is achieved with a variety of material applicability area and high quality clad track deposition with good mechanical properties. After development of this process in 1995, lot of researchers for several years work on various aspects of high quality deposition with dimensional accuracy such as good clad geometry, clad height, and microstructure study of the mechanical properties. Through this paper on the basis of literature survey an attempt has been made to focus on proper selection of the set up configuration for direct laser metal deposition to fulfill the requirement and helps to achieve high quality deposition.
The effect of dopamine (DA) on the release of cytokines from activated human T cells has been evaluated to analyze the mechanism by which physiological concentration of dopamine inhibits T cell ...proliferation. Dopamine inhibited anti-CD3 mAb-induced release of both Th1 and Th2 cytokines, IL2, IFN-γ and IL4 from T cells by specific class of dopamine receptors. This action of dopamine was mediated by a new mechanism. Dopamine suppressed non-receptor tyrosine kinases, Lck and Fyn expression which are the initial and pivotal signaling steps in T cell receptor (TCR) mediated different down stream signaling cascades, leading to cytokine release and subsequent clonal expansion of these immune effector cells.
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