Faculty Publications
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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 material properties of Mg-8%Al-0.5%Zn alloy after the combined processes of multi-direction forging and equal channel angular pressing(Institute of Physics, 2019) Naik, G.M.; Anjan, B.N.; Narendranath, S.; S Satheesh Kumar, S.; Preetham Kumar, G.V.Establishing the novel microstructure is an effective method to accelerate the applications of magnesium and its alloys. In this work, an Mg-8%Al-0.5%Zn alloy (AZ80 Mg) with ultra-fine-grain (UFG) size of ?1.29 ?m was achieved by the combined processes of multi-directional forging (MDF) and equal channel angular pressing (ECAP). The achieved ultra-fine grain structure made the Mg alloy, owing to inclusive performance as the structural material. The AZ80 Mg alloy with MDF 6 pass followed by two pass ECAP has superior mechanical properties such as ultimate tensile strength (UTS) of 352 MPa and elongation of 11% when compared to as-received Mg alloy. Also, an unprocessed Mg alloy showed the corrosion rate of a 13.28 mm y?1, the corrosion rate of processed Mg alloy could be further decelerated through a change of microstructure obtained from combined processes of MDF and ECAP. This study outstandingly obtained a 94% reduction of corrosion rate after MDF-3P followed by an ECAP-2P (0.77 mm y?1) process compared to as-received Mg alloy. © 2019 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 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.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).