Faculty Publications
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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.Item Analysing the combined effect of crystallographic orientation and grain refinement on mechanical properties and corrosion behaviour of ECAPed ZE41 Mg alloy(National Engg. Reaserch Center for Magnesium Alloys, 2020) Sekar, S.; Narendranath, S.; Desai, V.Two step equal channel angular pressing carried out on as cast ZE41 Mg alloy resulted in a remarkable grain refinement. As compared to grain size of 46 µm in as cast sample, refinement upto 2.5 µm was achieved after 8th pass equal channel angular pressing (ECAP). The combined effect of crystallographic orientation and grain refinement was investigated by analysing the mechanical properties and corrosion behaviour of ZE41 Mg alloy using electron back scattered diffraction (EBSD). The first stage comprises of 1st, 2nd, 3rd and 4th passes at a processing temperature of 300 °C while the 5th, 6th, 7th and 8th passes were ECAPed at 275 °C in second stage. The mechanical properties of ZE41 Mg 158 yield tensile strength (YTS), 230 ultimate tensile strength (UTS) and 7% elongation in as cast condition is enhanced to 236 YTS, 295 UTS and 19.76%, respectively, after first stage ECAP. The yield tensile strength deteriorated due to the effect of texture predominating grain refinement during the second stage ECAP. The corrosion resistance of ZE41 Mg was significantly enhanced by ECAP and is inferred from electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation results .The role of microstructure was minimal on corrosion behaviour of ZE41 Mg due to extra resistance when tested in 0 M NaCl. However, the influence of grain refinement greatly influenced the improvement in corrosion resistance of ZE41 Mg rather than crystallographic orientation observed from EBSD. In contrast, the crystallographic orientation predominated the effect of grain refinement during ZE41 Mg corrosion in chloride containing (0.1 M and 1 M NaCl) solutions. From the observation of results it is found that equal channel angular pressing has the dual advantage of improving mechanical properties and corrosion resistance of ZE41 Mg alloy. © 2020Item A study on the influence of WEDM parameters on surface roughness, kerf width, and corrosion behavior of AZ31B Mg alloy(Elsevier Ltd, 2022) Chaitanya, V.H.; Sekar, P.; Narendranath, S.; Balaji, V.Wire electric discharge machining (WEDM) is a nontraditional machining process where the material is removed by the spark erosion technique. This technique is used to machine AZ31B, a biodegradable Magnesium alloy. In the present work impact of WEDM input parameters, namely pulse on time (Ton), pulse off time (Toff), servo voltage (SV), and wire feed (WF) on response characteristics is studied. The response characteristics considered are kerf width (KW), surface roughness (SR), and corrosion rate (CR). L9 orthogonal array by Taguchi's is employed as the design of experimentation. Taguchi's analysis implied that TON is the most influencing input parameter on the response characteristics. At a relatively lower TON setting (105 μs), comparatively lesser kerf width (335.894 μm), lower surface roughness (3.069 μm), and lower corrosion rate (0.95 mm/year) are exhibited by the machined specimens. From the main effects plots using signal-to-noise ratios, it is understood that the values of response characteristics increased with an increase in TON value. It is due to the increase in discharge at the more pulse on time duration. It is also understood that a surface with relatively better surface finish exhibited better corrosion resistance. With the help of regression equations, the relation between response characteristics and input parameters is built. © 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.Item Effect of Wire-EDM textures on corrosion performance of Bio-Degradable Mg alloy(Elsevier B.V., 2024) Aswith Babu, I.; Kumar Manjhi, S.; Sekar, P.; Narendranath, S.; Balan, A.S.S.Magnesium (Mg) is the most suitable material for biodegradable implant applications owing to its nontoxic behaviour and comparable Young's modulus to human bone. However, poor corrosion resistance limits its application. Therefore, surface texturing can be a more suitable and cost-effective technique to mitigate these issues. Hence, wire electric discharge machining (WEDM) is used to create various textures (wavy texture, microchannels, and micro-pillars) and investigate their influence on the corrosion resistance of Mg-Zn-Ca alloy. The results revealed that micropillar texture exhibited significantly lower surface roughness (Ra = 1.049 µm) and a higher contact angle indicative of hydrophobicity (130.3°), resulting in superior corrosion resistance (corrosion rate: 0.816 mm/year) compared to other textures and standard WEDM surfaces. These findings suggested that textured surfaces generated through WEDM hold the potential for enhancing the corrosion resistance of biodegradable Mg implants. © 2024 Elsevier B.V.Item Machining Parameter Optimization of Wire Electrical Discharge Machining for Ni50.3Ti29.7Hf20 Alloy Using TOPSIS and Grey Wolf Optimization Technique(Springer, 2025) Bhaskar, M.; Balaji, V.; Narendranath, S.; Sahu, R.K.Ni50.3Ti29.7Hf20 is an alloy with shape memory characteristics that can withstand high temperatures. It possesses remarkable strength, hardness, and exceptional corrosion resistance. SMAs are well-suited for various applications, including automotive sensors, automobiles, aerospace technologies, robotics, actuators, and MEMS devices. However, its unique properties make it difficult to machine using conventional methods. Wire EDM is an unconventional machining process suited for difficult-to-machine materials like Ni-Ti-Hf alloy, providing high accuracy and precision and minimizing the risk of material damage. This paper focuses on the optimization of machining parameters, namely Discharge time (PON), Pause time (POFF), Gap voltage (GV), and Wire travel speed (WS) during WEDM of Ni-Ti-Hf shape memory alloy utilizing the TOPSIS and GWO techniques. The aim is to obtain optimal machining parameters for improving the machined Ni-Ti-Hf alloy’s material removal rate (MRR) and surface roughness (Ra). The optimal machining parameters from GWO were PON = 123.8 µs, POFF = 50 µs, WS = 2, and GV = 25. The predicted values of material removal rate and surface roughness are 4.22 mm3/min and 3.62 µm, respectively. The experimental verification demonstrates the proposed optimization approach's effectiveness, as the predicted values correlate strongly with the actual values. © ASM International 2023.