Faculty Publications
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Item Influence of Chloride Content and Exposure Time on Corrosion Behavior of AZ80 Wrought Mg Alloy(Springer Nature, 2020) Gote, G.D.; Naik, G.M.; Narendranath, S.This study aims to investigate the corrosion behavior of wrought AZ80 magnesium alloys in different chloride ion concentrations and exposure time. During the study, the effect of exposure time and chloride content on the corrosion resistance of AZ80 wrought Mg alloy has been studied with 2, 3.5, and 5 wt% NaCl aqueous solution for 12 h and 24 h exposure time. Charge transfer resistance for each sample was established using the Nyquist plot and corrosion rate obtained from polarization curve by adopting Tafel extrapolation method. Corrosion morphology was examined using scanning electron microscopy and XRD. The study revealed that corrosion product layer formed at initial stage was observed unstable after short exposure time which results in decrease in corrosion resistance at initial stage. An increase of chloride content in aqueous environment reduces the corrosion resistance of AZ80 wrought Mg alloy. © 2020, Springer Nature Singapore Pte 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 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 Corrosion of ECAPed magnesium alloys and its background: A Review(Chulalognkorn University, 2019) Naik, G.M.; SannaYellappa, N.; Kumar, S.S.S.The aim of this review article is to provide a brief mechanistic overview of magnesium alloys, equal channel angular pressing and corrosion behavior of un-ECAPed and ECAPed Mg alloys. The considerate of the corrosion processes of ECAPed Mg alloys builds upon interpretation of the corrosion of fine-grain magnesium alloys. This provides an understanding of the effect of grain size on corrosion of Mg alloys. This deep understanding is essential as a foundation if we are to produce corrosion-resistant magnesium alloys. Considerable has previously been accomplished, but there is enormous scope for development. This present concise review can provide a foundation for further, much desirable research. © 2019 Chulalognkorn University.Item Recent progress in equal channel angular pressing of magnesium alloys starting from Segal's idea to advancements till date – A review(KeAi Publishing Communications Ltd., 2023) Sekar, S.; Naik, G.M.; Narendranath, S.; Desai, V.Lightweight materials with high strength and ductility have immense potential in revolutionizing the automobile, aerospace, bio-medical and defence sector. Magnesium and its alloys are the candidates that are best suited for application in above mentioned sectors. However, achieving combination of properties such as high strength, good ductility and relatively better corrosion resistance in Mg alloys is still challenging. Indeed, equal channel angular pressing (ECAP) is one of the promising techniques that simultaneously enhances the mechanical properties and corrosion behaviour. In this review, an effort has been made to address the influence of ECAP on microstructure, mechanical properties, corrosion and galvanic corrosion of magnesium and its alloys. The reason for deviation of Mg alloys from Hall Petch relation is clarified. The necessity of tailoring the microstructure of Mg alloys in order to achieve desired properties is elucidated. In addition, the recommendations and future directions derived from summary and outlook of review are critiqued. © 2022 The AuthorsItem Effect of grain refinement on the performance of AZ80 Mg alloys during wear and corrosion(Techno-Press info@techno-press.com, 2018) Naik, G.M.; Gote, G.D.; Narendranath, S.; Satheesh Kumar, S.S.Magnesium and its alloys are attracted towards all engineering applications like automotive, marine, aerospace etc. due to its inherent high strength to weight ratio. But, extensive use of Mg alloys is limited to the current scenario because of low wear and corrosion resistance behavior. However, equal channel angular press is one of the severe plastic deformation technique which has been effective method to improve the wear and corrosion resistance by achieving fine grain structure. In this study, the effect of grain refinement on wear and corrosion resistance of AZ80 Mg alloys were investigated. The wear behavior of the coarse and fine-grained Mg alloys was examined through L9 orthogonal array experiments in order to comprehend the wear behavior under varies control parameters. It was shown that ECAPed alloy increased the wear and corrosion resistance of the Mg alloy through the formation of fine grain and uniform distribution of secondary beta - phase. Also, the performance of AZ80 Mg alloy for these changes was discussed through SEM morphology. © 2018 Techno-Press, Ltd.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.Item Effect of ECAP Die Angles on Microstructure Mechanical Properties and Corrosion Behavior of AZ80 Mg Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Naik, G.M.; Narendranath, S.; Kumar, S.S.S.In this article, the effect of channel angles on material properties was investigated during equal channel angular pressing of AZ80 magnesium alloy using processing route R at 325 °C processing temperature. Channel angles of 90° and 110° and common corner angle 30° have been considered for this study. It has been revealed that the channel angle has a significant influence on deformation homogeneity, microhardness, ultimate tensile strength, ductility and corrosion behavior of Mg alloys. Investigation with reference to as-received AZ80 Mg alloy indicates 18.47% improvement in UTS and 76.07% enhancement in ductility after processing through 3P-90° and 2P-110° ECAP, respectively. Also, the corrosion rate reduces to 89.47% after processing the sample with 3P-110° ECAP die. © 2019, ASM International.Item Bio-corrosion impacts on mechanical integrity of ZM21 Mg for orthopaedic implant application processed by equal channel angular pressing(Springer, 2021) Sekar, P.; Nyahale, M.B.; Naik, G.M.; Narendranath, N.; Prabhu, A.; Rekha, P.D.The mechanical integrity of rolled ZM21 Mg was improved by equal channel angular pressing (ECAP) to function as a potential biodegradable bone screw implant. Electron backscattered diffraction (EBSD) revealed deformed grains of 45 µm observed in rolled ZM21 Mg. They were transformed to equiaxed fine grains of 5.4 µm after 4th pass ECAP. The yield strength of rolled and ECAPed ZM21 Mg alloys were comparable. In contrast, 4th pass ZM21 Mg exhibited relatively higher elongation when compared to rolled sample. The mechanical properties of rolled and ECAPed ZM21 Mg were dependant on both grain refinement and crystallographic texture. The rolled and 4th pass ECAPed tensile samples exhibited nonlinear deterioration of mechanical properties when tested after 7, 14, 21 and 28 days immersion in Hank’s solution. The evaluation signifies that regardless their processing condition, ZM21 Mg alloys are suitable for surgical areas that requires high mechanical strength. In addition, the 4th pass ECAP samples were viable to MG-63 cells proving themselves to be promising candidates for future in vivo studies. [Figure not available: see fulltext.] © 2021, The Author(s).