Conference Papers
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Item Microstructural and Hardness evolution of AZ80 alloy after ECAP and post-ECAP processes(Elsevier Ltd, 2018) Naik, G.M.; Gote, G.D.; Narendranath, S.This research paper investigates the microstructure evolution and hardness variation of wrought AZ80 magnesium alloy after each ECAP passes. The strengthening effect of AZ80 alloy was examined after post-ECAP aging treatment. Alloys were severely deformed through equal channel angular press at 533K using route Bc with a die channel angle (φ) 1100 and corner angle (ψ) 300. Subsequently, the microstructural characterization was studied using optical microscope (OM) and scanning electron microscope (SEM). Further, post-ECAP aging treatment at 523K for 6h and 12h was performed and microhardness of the specimens was measured. It was found that the grain refinement through thermo-mechanical processing of ECAP and Post-ECAP treatment significantly improves the microhardness of the Mg alloy, which directly influences the properties of wrought AZ80 magnesium alloy. © 2018 Elsevier Ltd. All rights reserved.Item An investigation on effects of wire-EDT machining parameters on surface roughness of INCONEL 718(Elsevier Ltd, 2019) Naik, G.M.; Anjan, B.N.; Badiger, R.I.; Bellubbi, S.; Mishra, D.This paper studied the effects of machining parameters on surface roughness of wire EDT of INCONEL 718 super alloy. The investigated machining parameters were rotational speed, pulse-on time, pulse-off time, servo voltage, wire feed rate and flushing pressure. Analysis of variance (ANOVA) technique was used to find out the most significant parameters affecting the surface roughness. Results from ANOVA show that pulse-on time is significant variables to surface roughness of wire-EDT INCONEL 718 alloy. The surface roughness of the test specimen increased as these variables increased. Lastly, regression model was developed using a regression method to formulate the machining parameters to the surface roughness. The developed model was validated with an optimal setting parameters and the maximum prediction error of the model was less than 8%. © 2019 Elsevier Ltd.Item Influence of ECAP processing routes on microstructure mechanical properties and corrosion behavior of AZ80Mg alloy(American Institute of Physics Inc. subs@aip.org, 2019) Naik, G.M.; Narendranath, S.; Kumar, S.S.S.Wrought magnesium alloys are a potential material for automobile, aerospace, marine and electronics industries because of less density, higher specific strength, damping characteristics and electromagnetic shielding properties. In spite of this interest, Mg alloys have not been extensively utilized owing to their poor mechanical behavior and corrosion resistance in comparison to other lightweight materials. However, the literature clearly indicated that mechanical behavior and corrosion performance of Mg alloys can be improved through equal channel angular pressing method. Therefore, In this paper made an attempt to examine the influence of ECAP processing route Bc and R on microstructure, mechanical properties and corrosion performance of AZ80Mg alloy at 390°C isothermal processing temperature. The microstructural and morphology analysis is made through OM and SEM respectively. The electrochemical polarization experiments was conducted to investigate the corrosion resistance of AZ80 alloy after processing it through route Bc and R. Results revealed that a significant increase in tensile strength, % elongation and corrosion resistance can be attained depending on the selected ECAP processing route. © 2019 Author(s).Item Effect of grain refinement on mechanical and corrosion behavior of AZ91 magnesium alloy processed by ECAE(Institute of Physics Publishing helen.craven@iop.org, 2019) Naik, G.M.; Narendranath, S.; Satheesh Kumar, S.S.AZ91 Mg alloys were processed by equal channel angular extrusion (ECAE) up to 4 passes through route-R. The increase in number of ECAE passes to yield fine-grain structure in the bulk Mg alloy with a more dislocation density, this enhances mechanical properties and corrosion resistance. Indeed, microstructural observations revealed an equiaxed and significant grain refinement after ECAE-4P, with a mean grain size (d) of ∼ 4.36μm. Further, the tensile strength, micro-hardness and corrosion resistance were also increased, however the elongation was reduced with the increasing of ECAE passes. The electrochemical polarization test in 3.5wt % NaCl solution revealed a noticeable enhancement in the corrosion resistance of ECAE processed AZ91 Mg alloy compared with the as-received Mg alloy. This is mainly due to grain refinement and distribution of secondary phase particles in Mg alloy matrix during ECAE-4P. © 2019 Published under licence by IOP Publishing Ltd.Item Microstructure and Corrosion behavior of wrought AZ80 Mg alloys after the combined processes of ECAP and Hot Rolling(IOP Publishing Ltd, 2019) Naik, G.M.; Gote, G.D.; Narendranath, S.; Satheesh Kumar, S.S.In the current work, wrought AZ80 Mg alloys were subjected to equal channel angular pressing (ECAP) followed by hot rolling (HR). Then, combined effects of ECAP and HR on microstructure and electrochemical corrosion behavior were investigated in 3.5wt.% NaCl solution. The microstructure and corrosion morphology study was made through optical and scanning electron microscope respectively. The results show that the use of hot rolling after ECAP significantly decreases the grain size compared to as-received and ECAP-4 pass processed Mg alloys. In addition, electrochemical impedance spectroscopy and potentiodynamic polarization results have shown that the hot rolling of AZ80 Mg alloy after ECAP exhibited lower corrosion current and higher corrosion resistance is due to fine grain microstructure and continuous and uniform distribution of secondary phases. This was evidently observed during this study. © Published under licence by IOP Publishing Ltd.Item The Role of Processing Temperature in Equal Channel Angular Extrusion: Microstructure Mechanical Properties and Corrosion Resistance(Springer Science and Business Media Deutschland GmbH, 2020) Naik, G.M.; Narendranath, S.; Satheesh Kumar, S.S.Equal channel angular extrusion, patented in Russia by V. M. Segal in 1977, has become a promising technique to enhance tensile strength and corrosion resistance of Mg alloys. It is believed that the processing temperature ensures the production of ECAE-processed billet without surface defects. Indeed, ECAE processing temperature affects microstructure, tensile behavior, and corrosion resistance of the material. Therefore, this chapter investigates the impact of ECAE pressing temperature on microstructure, mechanical behavior, and corrosion resistance of AZ80 Mg alloys. The processing temperature of 533 and 663 K was selected based on the recrystallization temperature of Mg alloys. As a result, the processing temperature has a substantial impact on material properties. The axial tensile strength and hardness decrease by 25.45% and 6.56%, respectively, due to thermal softening of materials. The corrosion resistance increases by 84% due to grain size reduction and distribution of secondary phases, when the ECAP-4P processing temperature is increased from 533 K to 663 K. © 2020, Springer Nature Singapore Pte Ltd.Item Microstructural and mechanical characterisation of Al-Zn-Mg-Cu alloy processed by multi-directional cryo-forging(Elsevier Ltd, 2021) Ramesh, S.; Anne, G.; Naik, G.M.; Jagadeesh, C.; Shivananda Nayaka, H.S.Aim of the present investigation is to study the microstructural and mechanical properties of Al-Zn-Mg-Cu alloy before and after multi-direction forging (MDF) at cryogenic condition up to 3 cycles. Microstructure evolution of specimen was examined using optical microscope and orientation imaging microscopy as well as X-ray diffraction. Mechanical properties were measured by tensile test and Vickers micro hardness. Microstructural investigation shows that after 3 cycle of MDF average grain size was reduced to 8 μm with low angle grain boundaries (LAGBs) and high dislocation density. Mechanical examination displays an improvement in hardness, yield strength and ultimate tensile strength is due to increases in grain boundaries and strain hardening effect. After 3 cycles of MDF process with cumulative strain ςΔϵ = 3.64 led to the formation of fine grain structure, and microhardness were observed to be 168 HV. © 2021 Elsevier Ltd. All rights reserved.Item Saltwater corrosion behaviour of equal channel angular pressed AZ80/91 Mg alloys(Elsevier Ltd, 2021) Hebbale, A.M.; Naik, G.M.; Badiger, R.I.; Bellubbi, S.; Patil, S.; Narendranath, S.In this study, AZ80/91 Mg alloys were used to comprehend the electrochemical corrosion behaviour of coarse-grained and fine-grained Mg alloys in different concentration of NaCl solution as well as in the marine environment. The inadequate studies of the corrosion response of ECAPed AZ80 and AZ91 Mg alloy in a different environment were noticed. Accordingly, the current research presents and compares the corrosion behaviour of AZ80/91 Mg alloys in 2.5 wt% NaCl, 3.5 wt% NaCl solution and Natural Sea Water. Influence of corrosion media on coarse and fine-grained AZ80/91 Mg alloys was discussed in the results and discussion section. Corrosion attack of AZ80/91 Mg alloys under the above environment, increased with increase in chloride ion concentration and decreased with the ECAP passes. © 2021 Elsevier Ltd. All rights reserved.Item Optimizing machining responses of homologous TiNiCu shape memory alloys using hybrid ANN-GA approach(Elsevier Ltd, 2022) Roy, A.; Sachin, B.; Raghavendra, T.; Rao, C.M.; Naik, G.M.; Soni, H.; Mashinini, P.M.; Narendranath, S.Fabrication of shape memory alloys using wire electro discharge machining (WEDM) has gained popularity over the last few years. Most widely used machining parameters of WEDM process are pulse on time (Øon), pulse off time (Øoff), servo voltage (σ) and wire feed (ω). WEDM responses like material removal rate (MR), surface roughness (SR), kerf width (KW) and recast layer thickness (LT) have been evaluated by researchers to determine machining characteristics and are also considered for this study. These machining responses determine the quality of machining and are majorly influenced by thermal conductivity and melting temperature of the WEDM workpiece. Actuation behavior of shape memory alloys is a function of phase transformation characteristics which in turn depends on elemental composition of the selected alloys. Therefore, dissimilar machining responses of Ti50Ni40Cu10 and Ti50Ni25Cu25 have been observed even though similar machining input values were used. This study utilized artificial neural network (ANN) mapping to establish WEDM response function – which was used as fitness function to perform multi objective optimization using genetic algorithm (GA). It was found that ANN successfully predicted machining responses of selected homologous alloys and GA helped in identifying suitable input parameter values to optimize machining responses. © 2022Item A study on dimensional analysis modeling of crater size during wire electrical discharge turning process by using Buckingham Pi theorem(Elsevier Ltd, 2022) Naik, G.M.; Hipparagi, M.A.; Bellubbi, S.; Roy, A.; Anjan, B.N.; Ramesh, S.; Narendranath, S.The investigation on material removal by thermal erosion of discrete spark and vaporization in wire electrical discharge turning process was made to understand the crater size variation on turned components. In this study the modelling is done to establish the relationship between dependent and independent variables through Buckingham's Pi-theorem, to predict the variations of crater diameter depending on physical and thermal properties, subsequently the dimensional model was validated by conducting experiments on wire-electrical discharge turning process for two distinct density variant materials such as Aluminium 6061 and INCONEL 718 super alloys. The density, enthalpy of vaporization, radius of spark, specific heat and other quantities effect on crater diameter have been discussed in this research paper. © 2022