Showing papers by "Satish V. Kailas published in 2018"

Multi-layer graphene reinforced aluminum –manufacturing of high strength composite by friction stir alloying

Abstract: The paper reports manufacturing of a multi-layer graphene embedded composite of aluminium alloys by direct exfoliation of graphite into graphene with the help of Friction Stir Alloying (FSA). The formation of this nano composite and optimization of the process parameters led to an approximately two-fold increase in the strength, without loss in ductility, due to the dispersion of the graphene in aluminium. The manufacturing process is scalable and cost effective as it uses graphite powder and aluminium sheets as the raw materials. The presence of graphene layers in the metal matrix was confirmed using Raman spectroscopy as well as TEM. The graphene sheet thickness was measured using AFM after extracting it from the composite. Molecular dynamic simulation results reveal the evolution of newer structures and defects that have resulted in the enhanced properties of the nano-composite. These findings open up newer possibilities toward efficient and scalable manufacturing of high strength high-ductility metal matrix based graphene nano-composites.

Environmentally friendly functional fluids from renewable and sustainable sources-A review

Abstract: Use of animal and plant based oils for lubrication dates back to history. Discovery of petroleum and subsequent improvements in the refining technologies replaced them with mineral oil based lubricants. Mineral oil is a fast depleting resource and is also considered as an environmental pollutant. Impact of mineral oil based lubricants and restrictive environmental regulations have increased interest in lubricants derived from natural resources. Vegetable oils being renewable, non-toxic and biodegradable have become the primary choice for environmentally sensitive and total loss lubricant applications ranging from hydraulic oils to grease. This study covers the technical viabilities associated with vegetable oil based lubricants in different applications. In the first part of this review eco labeling, environmental regulations, source, composition and availability of vegetable oils are discussed. In the later part of review, performance evaluation of vegetable oils in different applications is covered. It has been noticed that straight vegetable oils have performed satisfactorily in metal forming; metal working, hydraulic applications and have shown promising performance as greases and engine oils. It was also observed that the selection of lubricant is based on price, then on performance, and lastly on environmental consideration. This would change only with the legislative pressure on restricting the use of petroleum based products and economic incentives for biobased lubricants in environmentally sensitive applications.

Two-pass friction stir welding of aluminum alloy to titanium alloy: A simultaneous improvement in mechanical properties

Abstract: During Friction Stir Welding (FSW) of aluminum (Al 2024) to titanium (Ti-6Al-4V), it is observed that titanium fragments at the interface get distributed in the weld nugget. These particles are both coarse and fine in size. Such a particle distribution, particularly due to presence of coarse particles, is expected to negatively impact the mechanical properties of the welds. In an effort to further fragment the coarse Ti particles, FSW was performed with an additional pass in the weld nugget region. Characterization was done using X-ray Micro-Computed Tomography (XCT), Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS), X-ray Diffraction and Electron Back-scattered Diffraction (EBSD) method. Tensile tests were performed to determine the mechanical properties of the weld. The Ti particles of various shapes and sizes were seen to be inhomogeneously distributed in the weld nugget even after the second pass. A detailed observation revealed that the larger particles (as flakes) were inhomogeneously distributed but the finer particles (more spherical) were homogeneously distributed in the weld nugget. It is observed that the weld after second pass contains a higher number of finer Ti particles. The variation in particles size and number fraction is due to the continuous fragmentation that occurs during the processing. Phase analysis reveals the formation of intermetallic compounds such as Al3Ti and AlTi in the welds. A detailed analysis discloses that the fraction of intermetallics in the weld nugget increases in the second pass when compared to the first pass. Aluminum in the weld nugget was substantially refined and recrystallized with grains consisting of mixed types of grain boundaries, which points to the mechanism of Continuous Dynamic Recrystallization (CDRX) through Dynamic Recovery (DRV). The EBSD analysis also reveals that the weld after second pass promotes the development of a high fraction of recrystallized grains (87%) when compared to that of first pass (78%). The second pass resulted in a significant improvement in the ultimate tensile strength (from 231 ± 8 MPa to 271 ± 6 MPa) and ductility (from 7.4 ± 0.3% to 9 ± 1.0%) of the weld. Such improvement in joint properties is analyzed considering the relative mechanical properties of the different zones across the weld nugget. A spring model has been employed to characterize the fracture behavior of the welds. This method and mechanism may be used to produce composite and dissimilar welds with unique mechanical properties by employing multi-pass processing and welding methodology.

Microstructure and Mechanical Properties of Friction Stir Process Derived Al-TiO2 Nanocomposite

Abstract: Aluminum-based composites have many advantages over their conventional counterparts. A major problem in such composites is the clustering of particles in the matrix. Friction stir processing (FSP) can homogenize particle distribution in aluminum-based composites. In this study, unannealed TiO2 particles were used to prepare Al-TiO2 nanocomposite using FSP. The TiO2 particles, about 1 µm, were dispersed into an aluminum matrix by 6 passes of FSP. The TiO2 particles were fractured by multiple FSP passes, leading to a nano-size particle distribution in the matrix. Nanoscale dispersion was confirmed by scanning electron microscopy and transmission electron microscopy. The fractured TiO2 particles reacted with the aluminum matrix to form Al3Ti intermetallic and Al2O3 ceramic. The progression of the Al-TiO2 reaction from the fourth to the sixth pass of FSP was revealed by x-ray diffraction. Due to the nanoscale dispersion, the yield and ultimate tensile strength of the composite increased to 97 and 145 MPa, respectively. Ductility of the composite decreased marginally compared to the as-received aluminum. As the dispersed particles pin dislocations, the strain-hardening rate of the composite was considerably increased and the same was seen in the Kocks-Mecking plot. The TiO2 particles are mechanically activated due to their fracture during FSP, hence leading to reaction with the matrix. The particle refinement and dispersion lead to a homogeneous matrix with higher strength.

Interfacial Microstructure and Mechanical Properties of Friction Stir Welded Joints of Commercially Pure Aluminum and 304 Stainless Steel

Abstract: In the present investigation, friction stir welding of commercially pure aluminum and 304 stainless steel was carried out at varying tool rotational speeds from 200 to 1000 rpm in steps of 200 rpm using 60 mm/min traverse speed at 2 (degree) tool tilt angle. Microstructural characterization of the interfacial zone was carried out using optical microscope and scanning electron microscope. Energy-dispersive spectroscopy indicated the presence of FeAl3 intermetallic phase. Thickness of the intermetallic layer increased with the increase in tool rotational speed. X-ray diffraction studies indicated the formation of intermetallic phases like FeAl2, Fe4Al13, Fe2Al5, and FeAl3. A maximum tensile strength of ~ 90% that of aluminum along with ~ 4.5% elongation was achieved with the welded sample at tool rotational speed of 400 rpm. The stir zone showed higher hardness as compared to base metals, heat affected zone, and thermo-mechanically affected zone due to the presence of intermetallics. The maximum hardness value at the stir zone was achieved at 1000 rpm tool rotational speed.

Effect of Zinc Interlayer in Microstructure Evolution and Mechanical Properties in Dissimilar Friction Stir Welding of Aluminum to Titanium

Abstract: The welding of aluminum (Al) and titanium (Ti) is difficult and challenging due to the differences in their chemical and physical properties, and the formation of brittle intermetallic phases. In the present experiment, a zinc (Zn) interlayer was used during friction stir welding of Al to Ti. The weld was characterized in detail to understand the mechanisms associated with microstructural evolution and improvement in mechanical properties of the weld. X-ray computed tomography results reveal three-dimensional distribution of particles and flakes of titanium in the weld nugget. It was also observed that Ti particles are inhomogeneously distributed in the weld and the distribution depends on their morphology. Such a distribution of Ti was informative in understanding material flow. In addition, the consolidation of Zn in the Al matrix reveals the nature of material flow in the weld nugget as well. The importance of the Zn interlayer and mechanism of phase formation was explored in this study. It was characterized that the mechanical mixing of Zn with Al and Ti alters phase evolution and restricts the formation of conventional Al3Ti intermetallic phase. The presence of zinc homogenizes elemental distribution and inhibits the formation of brittle intermetallic phases, which leads to a substantial improvement in mechanical properties of the weld.

Studying the lubricity of new eco-friendly cutting oil formulation in metal working fluid

Abstract: This paper aims to formulate a new metal working fluid (MWF) composition including some eco-friendly emulsifiers, corrosion inhibitor, biocide, and non- edible vegetable oil (castor oil) as the base oil. To achieve this aim, five MWFs with different hydrophilic–lipophilic balance (HLB) value as 10, 9.5, 9, 8.5 and 8 were prepared to identify the optimum HLB value that gives a highly stable oil-in-water emulsion. The performance of castor oil based MWF was evaluated using tool chip tribometer and drill dynamometer. The surface morphology of steel disc and friction pin was performed using scanning electron microscope (SEM) and 3D profilometer. The results revealed that the use of the prepared cutting fluid (E1) caused the cutting force to decrease from 500 N for dry high-speed steel sample to 280N, while the same value for a commercial cutting fluid (COM) was recorded as 340 N at drilling speed and cutting feed force as 1120 rpm and 4 mm/min., respectively.,A castor oil-based metalworking fluid was prepared using nonionic surfactants. The composition of the metalworking fluid was further optimized by adding performance-enhancing additives. The performance of castor oil based MWF was analyzed using Tool chip tribometer and Drill dynamometer. The surface morphology of steel ball and a disc was done using 3D profilometer and SEM.,Studies revealed that castor oil-based MWF having Monoethanolamine (MEA) as corrosion inhibitor was found to be highly stable. The drilling dynamometer and tool chip tribometer studies showed that castor oil-based MWF performance was comparable to that of commercial MWF.,This study aims to explore the performance of the castor oil based metalworking fluid (MWF) using tool chip tribometer and drill dynamometer.,The conventional MWFs are petroleum derives and are unsustainable. Use of non-edible plant-based oils for preparing the MWF will not only be conserved environment but also add value addition to agricultural crops.,The social Implications is aiming to decrease the environmental impact that results from the using of mineral cutting fluids.,The originality of this work is to replace the mineral oil and synthetic oil based cutting fluids with more eco-friendly alternatives one. In addition, the investigation will focus on developing functional additives required for cutting fluids which are environmentally benign.

Wear Behavior of Friction Stir Processed NAB Alloys in Marine Environment

Abstract: Nickel Aluminum Bronze (NAB) is a copper based alloy with Nickel (~7%), Iron (~7%) and Aluminum (~13%) as main alloying elements, together with other elements like Manganese. Due to superior mechanical properties and corrosion resistance, it is widely used in marine applications, and in aerospace industry and architecture. Friction Stir Processing (FSP) is a materials processing operation in which a rotating non-consumable tool is thrust into the workpiece (Fig. 1), causing localized heat generation, plastic flow, and churning, altering the microstructure and properties of the workpiece material. The process causes high strain, strain rate, and temperature gradients within the narrow zone subjected to FSP. FSP has been found to improve the mechanical properties of NAB alloys [1-3] and particulate addition into the processing zone during the FSP process has been found to enhance them [4, 5]. In a recent development [6], a novel in-situ method for incorporating nanoscale ceramic particles during FSP has been found to improve the micro-hardness significantly. While processing, this alloy using FSP, the ceramic phase was introduced as an organic-polymer precursor (a class of silicon based polymer known as polysilazanes) that would undergo pyrolysis at higher temperatures thereby converting it into a ceramic phase, known as polymer-derived ceramic (PDC) which was found to result in increased hardness (details of the process can be got from [6]). Previous studies related to wear behavior of NAB alloys concentrated on the synergistic effect of erosion and corrosion suffered by NAB alloys in saline environment, erosion-corrosion