Faculty Publications
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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 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 Annealing and Aging Treatment on Pitting Corrosion Resistance of Fine-Grained Mg-8%Al-0.5%Zn Alloy(Springer, 2019) Naik, G.M.; Narendranath, S.; Satheesh Kumar, S.S.; Sahu, S.In order to study the influence of plastic deformation, annealing and aging treatment on pitting corrosion, the AZ80Mg alloy was subjected to equal-channel angular pressing (ECAP) by route R at 325°C for up to 4 ECAP passes (P) and annealing conditions of 523 K, 623 K and 723 K followed by aging treatment at 6 h and 12 h. A microhardness and corrosion study was accomplished and microstructural evolution was recorded using optical microscopy (OM), scanning electron microscopy and electron backscatter diffraction (EBSD). OM and EBSD analysis showed that a fine-grain microstructure with average grain sizes of 32.87 µm and 6.35 µm was achieved after 2P and 4P of ECAP, respectively. During annealing and aging treatment, the fine-grain Mg alloy revealed that the maximum microhardness and improved corrosion resistance were observed mainly due to redistribution of ?-secondary phases. Specifically, 12 h aged specimens at 523 K represented maximum microhardnesses of about 85 Hv and 87 Hv for ECAP-2P and -4P, respectively. Also, 12 h aging at 723 K appeared preferable for accomplishing enhanced corrosion properties. © 2019, The Minerals, Metals & Materials Society.