Journal Articles
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Item Effect of equal channel angular pressing on AZ31 wrought magnesium alloys(National Engg. Reaserch Center for Magnesium Alloys zhangdingfei@cqu.edu.cn, 2013) Muralidhar, A.; Narendranath, S.; Shivananda Nayaka, H.AZ31 wrought magnesium alloys are light weight materials which play an important role in order to reduces the environmental burdens in modern society because of its high strength to weight ratio, corrosion resistance, and stiffness and machinability. Applications of this material are mainly in structural component i.e., in constructions, automobile, aerospace, electronics and marine industries. In the present work, the microstructure characterization of the AZ31 alloys up to four ECAP passes at temperature of 573 K was observed for route Bc. Average grain size of the material was reduced from 31.8 ?m to 8 ?m after four ECAP passes. Mechanical properties of the alloy improved with increase in number of ECAP passes. Moreover, X-ray diffraction analysis was carried out for as received and ECAP processed material. © 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University.Item Influence of Route-R on wrought magnesium AZ61 alloy mechanical properties through equal channel angular pressing(National Engg. Reaserch Center for Magnesium Alloys zhangdingfei@cqu.edu.cn, 2014) Muralidhar, M.; Narendranath, S.A new fundamental route entitled 'Route-R' is introduced to refine the grains in the material through Equal Channel Angular Pressing (ECAP) process. In route R, specimen is inverted to the original position in each ECAP pass. In the present work, AZ61 alloy is processed using ECAP process for three different fundamental routes mainly route A, route Bc, and route R. ECAP experiment is carried out on AZ61 alloy at lower temperature of 483 K up to two passes. Microstructural characterization is evaluated on unECAPed and ECAPed specimens for three routes. Average grain size of the alloy is to be reduced from 66 ?m to 16 ?m, 14.1 ?m and 10 ?m for route A routes Bc, and route R respectively. Vickers microhardness of the alloy is found to be 60 HV for as received material. This microhardness of the alloy is increased to 71 HV, 72 HV, and 74 HV for route A, route Bc, and route R respectively. Mechanical properties of the AZ61 alloy are observed to be route R is providing maximum YS, UTS, and percentage elongation than other route A and route Bc. Tensile fracture topography of the specimen is analyzed using three different routes for two passes. © 2014 National Engineering Research Center for Magnesium Alloys of China, Chongqing University.Item Effect of combined grain refinement and modification on microstructure and mechanical properties of hypoeutectic, eutectic and hypereutectic Al-Si alloys(Inderscience Publishers, 2015) Shivaprasad, C.G.; Kiran Aithal, K.; Narendranath, S.; Desai, V.; Mukunda, P.G.The effect of melt treatment owing to the combined addition of grain refiner and modifier on the microstructure and mechanical properties of Al-Si alloys having 7% (hypoeutectic), 12% (eutectic) and 15% silicon (hypereutectic) is studied. 1 wt. % of Al-1Ti-3B Master alloy was used as grain refiner. For modification of eutectic Si, 0.2 wt. % of Al-10Sr Master alloy was added to hypoeutectic alloy and 0.4 wt. % is added to eutectic alloy as well as hypereutectic alloy. Furthermore, refinement of primary Si in hypereutectic alloy was achieved by addition of 0.04 wt. % of phosphorus. The goal of this investigation is to determine the influence of combined addition of grain refiner and modifier on mechanical properties and qualitatively correlate with the microstructural changes. © 2015 Inderscience Enterprises Ltd.Item Evaluation of WEDM performance characteristics of Inconel 706 for turbine disk application(Elsevier Ltd, 2015) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 is a newly developed superalloy, which offers high mechanical strength alongwith easy fabricability thus making it suitable for turbine disk applications. Although Inconel 706 exhibits a substantial increase in stress rupture and tensile yield strength compared to other superalloys, its conventional machining yields poor surface finish and low dimensional accuracy of the machined components. Hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed and various performance attributes such as material removal rate (MRR), surface roughness (SR), recast surface, topography, microhardness, microstructural and metallurgical changes of the machined components have been evaluated. The experimental results revealed that servo voltage, pulse on time, and pulse off time greatly influence the MRR and SR. Due to high toughness of Inconel 706, no micro cracks were observed on the machined surface. Micro voids and micro globules are significantly reduced at low pulse on time and high servo voltage. But, there is a propensity of thick recast layer formation at high pulse on time and low servo voltage. EDAX analysis of recast surface exposed the existence of Cu and Zn which have migrated from the brass wire. The subsurface microhardness was changed to 80. ?m due to significant thermal degradation. © 2015 Elsevier Ltd.Item Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected. © 2016, ASM International.Item Effect of wire diameter on surface integrity of wire electrical discharge machined Inconel 706 for gas turbine application(Elsevier Ltd, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 superalloy has established itself in the field of gas turbine industry because of its easy fabricability combined with high mechanical strength. Due to its high stress rupture and tensile yield strength, conventional machining of this superalloy exhibits poor surface and low dimensional accuracy of the machined components. It is well known that most of the gas turbine components include complex shaped profile with high precision and hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed to achieve the feasibility in manufacturing of complex shaped components for gas turbine application. In the current investigation, the effect of wire diameter on WEDM performance characteristics such as cutting speed, surface roughness, surface topography, recast layer formation, microhardness, microstructural and metallurgical changes have been evaluated. It was investigated that smaller diameter wire is advantageous over the larger diameter wire since it improves productivity as well as surface quality of the machined components under the same settings of control parameters. In addition, smaller diameter wire has shown comparatively lower recast layer thickness, minimum hardness alteration and shorter manufacturing time. The XRD result has confirmed the presence of residual stress within WED machined component. © 2016 The Society of Manufacturing EngineersItem Influence of ageing time on hardness, microstructure and wear behaviour of AISI2507 super duplex stainless steel(Institute of Physics Publishing helen.craven@iop.org, 2017) Davanageri, M.; Narendranath, S.; Kadoli, R.The effect of ageing time on hardness, microstructure and wear behaviour of super duplex stainless AISI 2507 is examined. The material was solution treated at 1050 °C and water quenched, further the ageing has been carried out at 850 °C for 30 min, 60 min and 90 min. The chromium (Cr) and molybdenum (Mo) enriched intermetallic sigma phase (?) were found to precipitate at the ferrite/ austenite interface and within the ferrite region. The concentration of intermetallic sigma phase (?), which was quantified by a combination of scanning electron microscopy and image analysis, increases with increasing ageing time, leading to significant increase in the hardness. The x-ray diffraction (XRD) and energy dispersive x-ray (EDX) was employed to investigate the element distribution and phase identification. Wear characterstics of the aged super duplex stainless steel were measured by varying normal loads, sliding speeds, sliding distance and compared with solution treated (as-cast) specimens. Scanning electron microscopy was used to assist in analysis of worn out surfaces. The outcomes suggested that the increase in percentage of sigma phase increases hardness and wear resistance in heat-treated specimens compared to solution treated specimens (as-cast). © 2017 IOP Publishing Ltd.Item Effect of Secondary Mg17Al12 Phase on AZ80 Alloy processed by Equal Channel Angular Pressing (ECAP)(Springer Netherlands, 2018) Muralidhar, M.; Narendranath, S.AZ80 alloy was subjected through Equal Channel Angular Pressing (ECAP) to refine the grains at three different temperatures 548 K, 573 K, and 623 K up to 4 passes for route Bc, where the specimen is rotated 90? counter-clockwise direction for each pass. In the present work, experiments have been continued with route Bc and the average grain size was obtained of 7 ?m, 9.5 ?m and 11.2 ?m for the temperatures of 548 K, 573 K, and 623 K respectively after 4 ECAP passes. The average grain size of the procured AZ80 alloy was found to be 44.5 ?m. Mechanical properties of AZ80 alloy have been improved to the corresponding various processing temperatures. X-ray diffraction studies have been done on a fourth ECAP processed specimen and compared with a zero pass specimen to know the phase transformation at different processing temperatures. Fracture behavior of each of the three materials was studied and it revealed brittle fracture by increasing the number of ECAP passes. © 2015, Springer Science+Business Media Dordrecht.Item Analysis and Optimization of WEDM Performance Characteristics of Inconel 706 for Aerospace Application(Springer Netherlands rbk@louisiana.edu, 2018) Sharma, P.; Dupadu, D.; Narendranath, S.Wire Electrical Discharge Machining (WEDM) has established itself for manufacturing of precise and complex shape components for aerospace application due to the high quality requirement of aerospace components such as normal residual stress, no cracks, no recast layer, no porosity; still there is a need to optimize the control parameter settings and evaluate the performance characteristics of the WEDM process. The experiments have been conducted on Inconel 706 which is a newly-developed superalloy specially for aircraft application. A hybrid approach has been used to optimize the material removal rate (MRR) as well as surface roughness (SR) and significant control parameters have been identified using analysis of variance (ANOVA). Microstructure analysis revealed the formation of microglobules, melted debris and microholes on the machined surface, but no microcrack was detected due to the high toughness of the alloy. Energy dispersive X-ray spectroscopy (EDAX) has been carried out to study the metallurgical changes in the WED machined surface. The topography analysis of the curved surface revealed the best surface quality of the machined component at low pulse on time and high pulse off time. A thick recast layer of 39.6 µm was observed at high pulse on time and low servo voltage. Microhardness of the machined surface was changed up to a depth of 70 µm due to cyclic thermal loading during the WEDM process. © 2017, Springer Science+Business Media Dordrecht.Item The impact of homogenization treatment on microstructure microhardness and corrosion behavior of wrought AZ80 magnesium alloys in 3.5 wt% NaCl solution(Institute of Physics Publishing helen.craven@iop.org, 2018) Naik, G.M.; Gote, G.D.; Narendranath, S.; Satheesh Kumar, S.S.This paper investigates the effect of homogenization treatment on microstructure, micro-hardness and corrosion behavior of AZ80 wrought Magnesium alloy. Homogenization at 523 K, 623 K, and 723 K were accomplished. Meanwhile samples were cooled in the furnace after 6 h and 12 h of diffusion annealing treatment. In this study, samples were characterized by using optical microscopy (OM) and scanning electron microscopy (SEM). Micro-hardness of the homogenized specimens were measured and electrochemical corrosion behavior of homogenized AZ80 alloy has been investigated. Attempt has been made to enhance both the hardness and corrosion resistance of the AZ80 Mg alloy by changing its microstructure during homogenization treatment. This investigation revealed that the hardness of Mg alloy is improved at 523 K-12 h holding time. It was also found that corrosion rates are minimum at higher homogenization temperature and lower holding time because of uniform distribution of secondary ?-phases in Mg matrix, evidently shown in the microstructure of the heat treated Mg alloy. As a result, the homogenization treatment at 723 K for 6 h is desirable to enhance the corrosion resistance. © 2018 IOP Publishing Ltd.