S. Das

Bio: S. Das is an academic researcher from Advanced Materials and Processes Research Institute. The author has contributed to research in topics: Alloy & Microstructure. The author has an hindex of 24, co-authored 31 publications receiving 2453 citations. Previous affiliations of S. Das include Council of Scientific and Industrial Research.

Solidification, structures, and properties of cast metal-ceramic particle composites

Abstract: Solidification synthesis of cast metal-ceramic particle composite materials by dispersing hard or soft ceramic particles (including microballoons) and short fibres in molten alloys before solidification is described. Microstructures synthesized using a variety of casting techniques such as gravity or pressure die casting, centrifugal casting, and squeeze casting are discussed. Techniques to obtain a selected distribution of dispersed particles in cast alloy matrices by controlling solidification parameters and inducing melt particle wettability are reviewed. These cast metal-ceramic particle composites represent low cost, high performance, tailor made substitute materials for a variety of automotive and electromechanical applications such as pistons, cylinder liners, bearings, and current collectors, resulting in savings of material and energy.

Effect of machining parameters on surface roughness and tool wear for 7075 Al alloy SiC composite

Abstract: In the present study, an attempt has been made to investigate the influence of cutting speed, depth of cut, and feed rate on surface roughness during machining of 7075 Al alloy and 10 wt.% SiC particulate metal-matrix composites. The experiments were conducted on a CNC Turning Machine using tungsten carbide and polycrystalline diamond (PCD) inserts. Surface roughness of 7075Al alloy with 10 wt.% SiC composite during machining by tungsten carbide tool was found to be lower in the feed range of 0.1 to 0.3 mm/rev and depth of cut (DOC) range of 0.5 to 1.5 mm as compared to surface roughness at other process parameters considered. Above cutting speed of 220 m/min surface roughness of SiC composite during machining by PCD tool was less as compared to surface roughness at other values of cutting speed considered. Wear of tungsten carbide and PCD inserts was analyzed using a metallurgical microscope and scanning electron microscope. Flanks wear of carbide tool increased by a factor of 2.4 with the increase of cutting speed from 180 to 240 m/min at a feed of 0.1 mm/rev and a DOC of 0.5 mm. On the other hand, flanks wear of PCD insert increased by only a factor of 1.3 with the increase of cutting speed from 180 to 240 m/min at feed of 0.1 mm/rev and DOC 0.5 mm.

A comparative corrosion behavior of Mg, AZ31 and AZ91 alloys in 3.5% NaCl solution

Abstract: The corrosion behavior of Mg, AZ31 and AZ91 has been evaluated in 3.5% NaCl solution using weight loss, electrochemical polarization and impedance measurements. Corrosion rate derived from the weight losses demonstrated the occurrence of steeply fast corrosion reaction on AZ91 alloy after three hours of immersion, indicating the start of galvanic corrosion. An increase of corrosion rate with immersion time was also observed for AZ31 but with lesser extent than AZ91 alloy. Whereas Mg metals showed a decrease of corrosion rate with immersion time, suggesting the formation of a protective layer on their surfaces. In contrast, the corrosion current density (I corr ) derived from the Tafel plots, exhibited their corrosion resistances in order of Mg > AZ91 > AZ31. Electrochemical charge transfer resistance (R ct ) and double layer capacitance measured by electrochemical impedance spectroscopy (EIS), are well in accordance with the measured I corr. EIS measurements with time and microstructural examination of the corroded and uncorroded samples are helpful in elucidation of results measured by electrochemical polarization.

Microstructure and wear of cast (Al-Si alloy)-graphite composites

Abstract: Graphite-particle-dispersed Al-Si alloys have potential for a variety of antifriction applications. In the present investigation, two Al-Si alloys (LM13 of near eutectic and LM30 of hypereutectic composition) were chosen as matrix alloys and composites were prepared by casting. Composites and matrix alloys were heat treated to produce different morphologies of silicon ranging from plate-like in die-cast alloys to near spherical in heattreated alloys. Wear tests were conducted, under both dry and partially lubricated conditions, with SAE30 oil on a pin-on-disc wear test apparatus, against a rotating steel (EN25) counterface. In partially lubricated wear tests, the sliding velocity V was varied from 1.4 to 4.6 m s −1 and the applied pressure P from 1.0 to 5.0 MPa. P - V limits of all matrix alloys and composites with different microstructures were evaluated. Heat-treated composites were found to possess superior wear properties (wear rate, seizure resistance and P - V limits) as compared with those of die-cast composites and matrix alloys. Worn surfaces of heat-treated composites showed the presence of a graphite film while those of die-cast alloys and composites showed surface fracture. The role of graphite particle dispersion and the morphology of silicon on the sliding wear behaviour is discussed.

Effect of matrix alloy and influence of SiC particle on the sliding wear characteristics of aluminium alloy composites

Abstract: This article presents an effect of matrix alloy and influence of SiC particle on the sliding wear characteristics of high strength aluminium alloys AA7010, AA7009 and AA2024, composites was examined under varying applied pressure and a fixed sliding speed of 3.35 m/s. The results revealed that the wear resistance of the composite was noted to be significantly higher than that of the alloy and is suppressed further due to addition of SiC particles. The overall observation among the matrix alloys, AA7010 alloy shows maximum wear resistance than that of the other, and can withstand the seizure pressure up to 2.6 MPa. The wear mechanism was studied through worn surfaces and microscopic examination of the developed wear tracks. The wear mechanism strongly dictated by the formation and stability of oxide layer, mechanically mixed layer (MML) and subsurface deformation and cracking. The overall results indicate that the high strength aluminium alloys and composite could be considered as an excellent material where high strength and wear resistance components are prime importance especially designing for structural applications in aerospace and general engineering sectors.

Particle reinforced aluminium and magnesium matrix composites

Abstract: Particle reinforced metal matrix composites are now being produced commerically, and in this paper the current status of these materials is reviewed. The different types of reinforcement being used, together with the alternative processing methods, are discussed. Depending on the initial processing method, different factors have to be taken into consideration to produce a high quality billet. With powder metallurgy processing, the composition of the matrix and the type of reinforcement are independent of one another. However, in molten metal processing they are intimately linked in terms of the different reactivities which occur between reinforcement and matrix in the molten state. The factors controlling the distribution of reinforcement are also dependent on the initial processing method. Secondary fabrication methods, such as extrusion and rolling, are essential in processing composites produced by powder metallurgy, since they are required to consolidate the composite fully. Other methods, suc...

Particulate reinforced metal matrix composites — a review

Abstract: The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) have made them attractive candidate materials for aerospace, automotive and numerous other applications. More recently, particulate reinforced MMCs have attracted considerable attention as a result of their relatively low costs and characteristic isotropic properties. Reinforcement materials include carbides, nitrides and oxides. In an effort to optimize the structure and properties of particulate reinforced MMCs various processing techniques have evolved over the last 20 years. The processing methods utilized to manufacture particulate reinforced MMCs can be grouped depending on the temperature of the metallic matrix during processing. Accordingly, the processes can be classified into three categories: (a) liquid phase processes, (b) solid state processes, and (c) two phase (solid-liquid) processes. Regarding physical properties, strengthening in metal matrix composites has been related to dislocations of a very high density in the matrix originating from differential thermal contraction, geometrical constraints and plastic deformation during processing.

Fundamentals and advances in magnesium alloy corrosion

Abstract: There remains growing interest in magnesium (Mg) and its alloys, as they are the lightest structural metallic materials Mg alloys have the potential to enable design of lighter engineered systems, including positive implications for reduced energy consumption Furthermore, Mg alloys are also emerging as viable biodegradable materials and battery electrodes In spite of the greatest historical Mg usage at present, the wider use of Mg alloys remains restricted by a number of inherent limitations, including vulnerability to corrosion, poor formability and low creep resistance This review covers recent research that has led to advances in Mg-alloy corrosion; including the application of contemporary methods for understanding Mg corrosion, the establishment of an electrochemical framework for Mg corrosion, illumination of alloying effects, and attempts at corrosion resistant Mg alloys A discussion drawing from many sources provides an unbiased focus on new achievements, as well as some contentious issues in the field The electrochemistry of Mg is reviewed in detail, including so-called anodic hydrogen evolution and cathodic activation This review also covers atmospheric corrosion, and biodegradable Mg alloys Finally, past and present trends in the field of Mg corrosion are reviewed, identifying knowledge gaps, whilst attempting to also identify future developments and directions

Production and mechanical properties of Al2O3 particle-reinforced 2024 aluminium alloy composites

Abstract: 2024 aluminium alloy metal matrix composites (MMCs) reinforced with three different sizes and weight fractions of Al2O3 particles up to 30 wt.% were fabricated by a vortex method and subsequent applied pressure. The effects of Al2O3 particle content and size of particle on the mechanical properties of the composites such as hardness and tensile strength were investigated. The density measurements showed that the samples contained little porosity, and the amount of porosity in the composites increased with increasing weight fraction and decreasing size of particles. Scanning electron microscopic observations of the microstructures revealed that the dispersion of the coarser sizes of particles was more uniform while finer particles led to agglomeration of the particles and porosity. The results show that the hardness and the tensile strength of the composites increased with decreasing size and increasing weight fraction of particles.

Metal matrix Composites

Abstract: This paper reviews the world wide upsurge in metal matrix composite research and development activities with particular emphasis on cast metal-matrix particulate composites. Extensive applications of cast aluminium alloy MMCs in day-to-day use in transportation as well as durable good industries are expected to advance rapidly in the next decade. The potential for extensive application of cast composites is very large in India, especially in the areas of transportation, energy and electromechanical machinery; the extensive use of composites can lead to large savings in materials and energy, and in several instances, reduce environmental pollution. It is important that engineering education and short-term courses be organized to bring MMCs to the attention of students and engineering industry leaders. India already has excellent infrastructure for development of composites, and has a long track record of world class research in cast metal matrix particulate composites. It is now necessary to catalyze prototype and regular production of selected composite components, and get them used in different sectors, especially railways, cars, trucks, buses, scooters and other electromechanical machinery. This will require suitable policies backed up by funding to bring together the first rate talent in cast composites which already exists in India, to form viable development groups followed by setting up of production plants involving the process engineering capability already available within the country. On the longer term, cast composites should be developed for use in energy generation equipment, electronic packaging aerospace systems, and smart structures.