Showing papers by "Satish V. Kailas published in 2017"

Microstructure, mechanical properties and shape memory behaviour of friction stir welded nitinol

Abstract: For the first time, NiTi shape memory alloy was successfully joined by Friction Stir Welding (FSW). The weld showed significant grain refinement without formation of detrimental phases. The yield strength of the weld joint increased by 17% as compared to the base metal without substantial change in shape memory behaviour.

Microstructure and Texture Evolution during Single- and Multiple-Pass Friction Stir Processing of Heat-Treatable Aluminum Alloy 2024

Abstract: Microstructure and crystallographic texture evolution during single- and multiple-pass friction stir processing (FSP) of an age-hardenable aluminum alloy 2024 (Al-Cu-Mg) was investigated. Multiple-pass experiments were carried out using two different processing strategies, multi-pass FSP, and multi-track FSP. Effect of a post-FSP heat treatment above and below the solutionizing temperature of the alloy was also studied. FSP experiments were carried out using an optimal set of parameters. Characterization tools used in the study include scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), electron probe micro-analyser (EPMA), and X-ray diffraction (XRD). Microstructural features indicate the occurrence of particle stimulated nucleation (PSN) assisted dynamic recrystallization (DRX) as the dominant microstructural evolution mechanism in the nugget zone. Geometrical coalescence occurred, leading to the formation of some larger grains in the nugget zone. Heterogenous micro-texture distribution was observed in the nugget zone with the bulk textures consisting of FCC shear texture components dominated by A (1)*/A (2)* and C. Microstructure and texture in the nugget zone remained stable after both routes of multiple-pass processing, demonstrating the possibility of FSP to produce bulk volume of fine-grained materials. Post-FSP heat treatment indicated the stability of microstructure and texture up to 723 K (450 A degrees C) owing to relatively lower strain energies retained after FSP.

End forming behaviour of friction stir processed Al 6063-T6 tubes at different tool rotational speeds

Abstract: The main aim of this work is to study the end forming behaviour of friction stir processed Al 6063-T6 tubes fabricated at different tool rotational speeds. Tube expansion, tube reduction and tube beading are performed on the friction stir processed and parent tubes. The load, thinning and hardness evolution during the end forming operations are evaluated. A rotational speed yielding moderate combination of initial hardness and hardening index of the friction stir processed zone governs the maximum load required during end forming. Tube reduction and tube beading need larger load because of tube thickening, as compared to tube expansion, in which tube thinning is witnessed. The friction stir processed zone of the processed tube undergoes larger thinning and thickening as compared to base material in tube expansion and reduction, respectively, while base material thickens more in tube beading. The hardness and strain hardening exponent difference govern such thickness evolution. Mechanical instabilities like failure of friction stir processed zone, wrinkling and overlapping of friction stir processed zone, and fine cracks development are seen during the end forming operations. The effect of rotational speed on the hardness and grain size distribution of friction stir processed zone is negligible. The hardness of processed zone is found to increase after end forming operations.

Machining of hardened AISI H-13 steel using minimum quantity eco-friendly cutting fluid

Abstract: Conventionally, cutting fluids are applied in the form of flood to improve machining performance and tool life. However, the use of cutting fluid has detrimental effect in the form of environmental pollution and occupational health hazard. Researchers are trying to develop alternate methodologies to reduce or eliminate cutting fluids during machining. In this study, indigenously developed eco-friendly green cutting fluid (GCF) is used with minimum quantity cutting fluid (MQCF) technique during machining of hardened AISI H-13 steel. Cutting force, feed force and centre line average (CLA) surface roughness were measured at different cutting conditions. Performance of MQCF was compared with flood coolant using GCF and dry machining. The morphology of the rake face of the tool was examined with optical microscope and scanning electron microscope. Cutting force, feed force, coefficient of friction and CLA surface roughness was reduced with MQCF using GCF as compared to flood coolant and dry machining.

Role of insert material on process loads during FSW

Abstract: In FSW, insert materials are often used to both control the loading conditions as well as to trace the nature of materials flow. This current study aims at understanding the role played by inserts materials by using two different materials, copper and tin as inserts. The copper and tin have higher and lower melting points respectively as compared to aluminum. The metal strips are sandwiched between aluminum plates and friction stir welded at two different rotational speeds. The process loads and torque were recorded during the welding and compared with that obtained for normal butt-welding of aluminum sheets. In the case of copper insert, copper gets distributed in the matrix and it is possible to trace the flow of copper inside the aluminum. In the case of tin, it melts during the welding. The molten tin is squeezed out of faying surface and coats tool shoulder. This lowers the friction and which in turn lowers the torque (55%) and the consequent heat generation. The resultant reduction of temperature in the weld leads to higher tangential and normal loads. Compared to the case without insert, the normal loads for FSW processing with tin insert were higher by 2.2 times and tangential loads were higher by 5.5 times.

Processing–Microstructure–Crystallographic Texture–Surface Property Relationships in Friction Stir Processing of Titanium

Abstract: Friction stir processing (FSP) is a solid-state technique for microstructural modification of metallic materials. The aim of this work is to establish processing–microstructure–texture–surface properties relationship in commercially pure titanium (cp-Ti) processed by FSP under different processing conditions. The effect of processing conditions on the microstructural changes and the evolution of crystallographic texture is systematically studied. The changes in the chemical composition of the passive surface layer are characterized by x-ray photoelectron spectroscopy. The corrosion behavior of cp-Ti after FSP is evaluated in simulated body fluid and is related to the microstructure, texture and composition of passive layer. Substantial grain refinement was observed after FSP. Shear type deformation texture evolved during FSP with dynamic restoration processes weakening the overall shear texture. The corrosion resistance improved after processing at lower rotational speed due to the presence of basal planes at the surface and the incorporation of TiN in the passive layer. The results of this study suggest that surface properties of cp-Ti like passive layer and corrosion resistance are altered by FSP and can be controlled using appropriate processing parameters.

A Study on Chemical and Lubrication Properties of Unrefined, Refined and Virgin Coconut Oil Samples

Abstract: In the present work four samples each of unrefined coconut oil (URCO), refined coconut oil (RCO) and virgin coconut oil (VCO) samples collected from different places were evaluated in terms of physicochemical and lubrication parameters. The physicochemical properties of URCO, RCO and VCO were analyzed in terms of kinematic viscosity, Fatty acid profile, Iodine number, Saponification number, free fatty acid, Peroxide value and flash point. The lubrication properties of the oil samples were compared with the aid of four ball tester. The study revealed that fatty acid profile of VCO samples was slightly different from that of URCO and RCO samples. The saponification and Iodine value of VCO samples was also slightly lower than that of URCO and RCO samples. The four ball test results showed that the average coefficient of friction under tested condition was slightly less for URCO and VCO samples when compared to RCO samples. This difference in frictional property was due to the presence of free acid in the URCO and VCO which acted as boundary lubricant. The increased wear observed with VCO and URCO samples was linked to the presence of peroxides.

Study on Effect of Aging and Aging Temperature on Frictional Properties of Coconut Oil Samples

Abstract: The present study evaluates the effect of aging and aging temperature on the frictional properties of Unrefined Coconut oil (URCO), Refined Coconut oil (RCO) and Virgin Coconut oil (VCO) samples using four ball tester. It was observed that the variations in the physicochemical properties of fresh URCO, RCO and VCO samples were attributed to the difference in their composition. This study showed that URCO, RCO and VCO samples followed same trend in their physicochemical and tribological properties when subjected to aging. The drop in flash point of aged oil samples with aging was attributed to the increased content of free fatty acids generated due to the degradation of triglyceride molecules. It was observed that the degradation of peroxide molecules has resulted in the stabilization in the peroxide content of URCO, RCO and VCO samples when aged at 100 C.

Evolution of In-Situ Nano-Pores during Friction Stir Processing of Polymer Derived Ceramic Reinforced Metal Matrix Composites

Abstract: Nano-porous ceramics have potential applications as diverse as biomedical implants, catalysis, and armors This work shows that insitu Nano-porous Polymer Derived Ceramics (PDC) can be produced in Metal Matrix Composites (MMCs) using solid state Friction Stir Processing (FSP) Direct insertion of cross-linked polymer into the metal by FSP in solid state is a significant step toward inserting different chemistry of polymer precursors to generate a variety of in-situ porous structures in Polymer Derived (PD)-MMC The PDC route is an efficient and cost effective way to produce SiCNbased PD-MMC and tailored pore architecture suitable for high temperature applications Microstructural observations indicate a uniform distribution of ~100 nm size pores in the ceramic phase after pyrolysis