Browsing by Author "Vijayan, V."

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A comparison of high temperature corrosion behaviour between uncoated, Ni-Cr-Mo and Ni-Cr-Al-Y coated 316 stainless steel in ZnCl2-KCl environment
(Elsevier B.V., 2025) Pooja, P.; Vijayan, V.; Ravishankar, K.S.; Madav, V.
High-temperature corrosion poses a significant challenge to the longevity and performance of materials in extreme environments. This study investigates the corrosion behavior of coated and uncoated 316 stainless steel (SS) in ZnCl2-KCl eutectic molten salt vapor at 600 °C. Contrary to expectations, the results indicate that uncoated 316 SS exhibits lesser corrosion compared to certain coated samples over prolonged exposure. Comprehensive analysis, including weight change measurements, electrochemical evaluations, and surface morphology examination, reveals the degradation mechanisms and the efficacy of coatings. Amongst the various materials used for study, NiCrMo coated 316SS showed least corrosion rate of 8.34 mpy and 3.2 mpy after 20 h and 100 h respectively. The findings provide insights into optimizing material protection strategies in harsh chloride containing molten salt environments. © 2025
A comprehensive review of friction stir welding parameters on Ti-6Al-4V alloy microstructure and mechanical properties
(Taylor and Francis Ltd., 2025) Rao, R.N.; Rao, S.S.; Vijayan, V.
Ti-6ALâ€“4 V alloy, is a widely recognised titanium alloy. It is responsible for over half of all applications involving titanium alloys, primarily due to its attractive mechanical and physical properties that make it a highly desirable material. For most applications, the vast majority of working components require permanent joining. The conventional fusion welding of titanium often leads to oxidation losses and increased brittleness. Friction stir welding improves weld quality by preventing heating the metal past its melting point. Despite the fact that Friction Stir Welding (FSW) of Ti6Al4V alloys has advantages over other welding methods, the process parameters have a major impact on the weld microstructure and mechanical properties. In most cases, a defect-free weld with the ideal microstructure can be achieved by selecting the best process parameters, such as the tool material, tool geometry, traverse speed, and rotational speed. This paper briefly reviews Ti-6Al-4 V alloy friction stir welding developments and understandings. Variation in friction stir welding process parameters like tool rotation and translation speed affects weld region microstructure constituents, defects, and mechanical properties. This paper establishes a crucial relationship between process variables, microstructure, defects, and mechanical properties. Summarising and tabulating recent developments for easy understanding and adoption is emphasised. Â© 2024 Informa UK Limited, trading as Taylor & Francis Group.
A comprehensive review of friction stir welding parameters on Ti-6Al-4V alloy microstructure and mechanical properties
(Taylor and Francis Ltd., 2025) Rao, R.N.; Rao, S.S.; Vijayan, V.
Ti-6AL–4 V alloy, is a widely recognised titanium alloy. It is responsible for over half of all applications involving titanium alloys, primarily due to its attractive mechanical and physical properties that make it a highly desirable material. For most applications, the vast majority of working components require permanent joining. The conventional fusion welding of titanium often leads to oxidation losses and increased brittleness. Friction stir welding improves weld quality by preventing heating the metal past its melting point. Despite the fact that Friction Stir Welding (FSW) of Ti6Al4V alloys has advantages over other welding methods, the process parameters have a major impact on the weld microstructure and mechanical properties. In most cases, a defect-free weld with the ideal microstructure can be achieved by selecting the best process parameters, such as the tool material, tool geometry, traverse speed, and rotational speed. This paper briefly reviews Ti-6Al-4 V alloy friction stir welding developments and understandings. Variation in friction stir welding process parameters like tool rotation and translation speed affects weld region microstructure constituents, defects, and mechanical properties. This paper establishes a crucial relationship between process variables, microstructure, defects, and mechanical properties. Summarising and tabulating recent developments for easy understanding and adoption is emphasised. © 2024 Informa UK Limited, trading as Taylor & Francis Group.
Achieving ultra-fine grains in Ti-6Al-4V alloy welds through pre-weld friction stir processing
(Elsevier B.V., 2024) Rao, R.N.; Rao, S.S.; Vijayan, V.
Titanium Ti-6Al-4V alloy, recognized for its exceptional strength, is extensively employed in the aerospace, biomedical, and automotive industries. Friction Stir Processing (FSP) has been found to enhance the overall performance, while friction stir welding (FSW) is recognized as the most effective technique for joining the Ti-6Al-4V alloy. This study focusses on the implementation of friction stir welding on a Ti-6Al-4V alloy that had previously undergone friction stir processing. The objective was to analyse the microstructure and mechanical characteristics. The examination using Electron Backscatter Diffraction revealed notable alterations in the microstructure, such as variations in grain size, misorientation angle, and grain boundaries. The proportion of high angle grain boundaries (HAGBs) on the advancing side and stir zone of the friction stir treated Ti-6Al-4V were 59 % and 66 %, respectively. Signifying grain refinement, grains measuring sizes between 0.83 ?m and 1.05 ?m were achieved as result of processing. Subsequent, friction stir welding resulted in about 50 % further decrease in grain size compared to base metal, with HAGBs comprising 71 % and 52 % at the advancing side and stir zone, respectively. As a result the Vickers micro hardness values increased to 397 ± 13Hv upon friction stir processing to 444 ±7Hv upon subsequent friction stir welding respectively. © 2024 The Authors
Assessment of latent heat and solid fraction of Al-22Si alloy using Newtonian and Fourier analysis techniques
(2015) Vijayan, V.; Prabhu, K.N.
Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined. � (2015) Trans Tech Publications, Switzerland.
Assessment of latent heat and solid fraction of Al-22Si alloy using Newtonian and Fourier analysis techniques
(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Vijayan, V.; Prabhu, K.
Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined. Â© (2015) Trans Tech Publications, Switzerland.
Computer aided cooling curve analysis and microstructure of cerium added hypereutectic Al-Si (LM29) alloy
(Springer India sanjiv.goswami@springer.co.in, 2014) Vijayan, V.; Prabhu, K.
Thermal analysis of LM29 alloy and Ce added LM29 alloys was carried out. The effect of cerium addition on solidification parameters and microstructural features of hypereutectic Al-Si (LM29) alloy was studied using Newtonian analysis technique. Thermal analysis parameters such as primary and eutectic phase nucleation and solidus temperatures were determined. The addition of Ce to LM29 alloy decreased the nucleation temperature of primary silicon and eutectic silicon. The microstructural examination of Ce added LM29 alloys revealed the presence of a polyhedral shaped Al-Si-Ce compound that might have caused the refinement of primary and eutectic silicon. The dendrite coherency point temperature of LM29 alloy was found to be suppressed on addition of Ce. © 2014 Indian Institute of Metals.
Corrosion behavior of high and low temperature austempered ductile iron (ADI) in iron ore slurry
(ASTM International, 2017) Aithal, P.M.; Vijayan, V.; Surendranathan, A.O.; Udupa, K.R.; Samuel, K.G.
Corrosion behavior of austempered ductile iron (ADI) and forged EN31 steel balls in a ground iron ore slurry was studied as a function of time in the slurry, while the microstructure of ADI developed due to different tempering temperature and tempering time. The corrosion rates of the grinding balls immersed in the iron ore slurry were determined using electrochemical analysis and weight loss methods. It was found that the pH of the iron ore slurry increased with time and the corrosion behavior was influenced by the pH of the slurry. The corrosion rate of forged EN31 steel balls increased with the increase in time and pH of the slurry, whereas the corrosion rate of ADI balls depended on the austempering treatment. In general, the forged EN31 steel ball offered better corrosion resistance than ADIs during the early stages of exposure in the slurry (low pH values of the slurry), but at higher pH values of the slurry, the ADIs yielded better corrosion resistance than forged EN31 steel balls. The ADI austempered at higher temperatures showed better corrosion resistance than the ones austempered at lower temperatures. © © 2017 by ASTM International.
Determining the solidification characteristics of Manganese bronze (MAB) alloy using computer-aided cooling curve analysis
(Elsevier Ltd, 2022) Pranesh; Mohammed Anas, S.; Johnson, S.; Jose, R.; Sachin, B.; Cadambi, S.; Vijayan, V.; Karinka, S.
Computer-aided cooling curve analysis (CACCA), known for its reliability and simplicity was used to study the material properties of manganese bronze (MAB) alloy. MAB alloy, due to its high strength and corrosion resistance, is a staple material for marine applications. Since the alloy is difficult to machine, non-heat treatable, and complex to fabricate, casting is the only cost-effective process of producing products of the material. As the literature is scant on the MAB's high-temperature properties, this study is aimed at determining the thermo-physical properties of the alloy required for casting simulation by carrying out Newtonian and Fourier analysis of the recorded temperature of the solidifying alloy from liquidus state. Â© 2022 Elsevier Ltd. All rights reserved.
Effect of Ce melt treatment on solidification path of ZA8 alloy
(Institute of Physics Publishing michael.roberts@iop.org, 2016) Sudheer, R.; Vijayan, V.; Prabhu, K.
The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique of thermal analysis. The solidification events were determined using cooling curve and its first derivative curve. The microstructure and chemical composition of various phases in the alloy were studied using EDS, SEM and XRD techniques. It was found that the addition of Ce did not cause formation of new phases. However, it hinders the nucleation of stable Î² dendrites in the alloy. The presence of Ce promotes the eutectoid phase transformation and increases the hardness of the alloy. Latent heat of solidification and heat of eutectoid transformation were found to increase on Ce addition. The upward solidification of the alloy against Cu chill was analysed. Chilling had significant influence on solidification parameters, and caused refinement of the microstructure. The addition of Ce to the melt had no effect during chill casting of the alloy.
Effect of cerium addition on casting/chill interfacial heat flux and casting surface profile during solidification of Al-14%Si alloy
(Institute of Physics Publishing michael.roberts@iop.org, 2016) Vijayan, V.; Prabhu, K.
In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast iron chills, to study the effect of Ce melt treatment on casting/chill interfacial heat flux transients and casting surface profile. The heat flux across the casting/chill interface was estimated using inverse modelling technique. On addition of 1.5% Ce, the peak heat flux increased by about 38%, 42% and 43% for copper, brass and cast iron chills respectively. The effect of Ce addition on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of an air gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line (Ra) and arithmetical mean of the absolute departures of the waviness profile from the centre line (Wa) were found to decrease on Ce addition. The interfacial gap width formed for the unmodified and Ce treated casting surfaces at the periphery were found to be about 35Î¼m and 13Î¼m respectively. The enhancement in heat transfer on addition of Ce addition was attributed to the lowering of the surface tension of the liquid melt. The gap width at the interface was used to determine the variation of heat transfer coefficient (HTC) across the chill surface after the formation of stable solid shell. It was found that the HTC decreased along the radial direction for copper and brass chills and increased along radial direction for cast iron chills.
Effect of chilling and cerium addition on microstructure and cooling curve parameters of Al-14%Si alloy
(Maney Publishing maney@maney.co.uk, 2015) Vijayan, V.; Prabhu, K.
Al-14%Si alloys, with and without cerium, were cast at varying cooling rates by solidifying them in a crucible and against chills. The effect of melt treatment and chilling on microstructure and cooling curve parameters of the alloy was assessed. Ce treated alloys solidified in clay graphite crucible at a slow cooling rate showed refinement of primary silicon and the formation of Al-Si-Ce ternary intermetallic compound. The addition of Ce to the alloy solidified against chills resulted in simultaneous refinement and modification of primary and eutectic silicon. Nucleation temperatures of both primary and eutectic silicon decreased on addition of cerium. The formation of the intermetallic compound decreased with increase in cooling rate, leading to the modification of the eutectic silicon. The increase in the degree of modification of the eutectic Si was associated with the decrease in the volume fraction of the intermetallic compound formed. © 2015 Canadian Institute of Mining, Metallurgy and Petroleum Published by Maney on behalf of the Institute.
Effect of Ni and Sr additions on the microstructure, mechanical properties, and coefficient of thermal expansion of Al-23%Si alloy
(Elsevier Ltd, 2021) Vijayan, V.; Ravi, M.; Prabhu, K.N.
In this paper, the combined and individual effect of strontium (Sr) and nickel (Ni) additions on the microstructure and mechanical properties of hypereutectic Al-23Si alloy was studied using an optical microscopy, universal tensile testing machine and Brinell hardness tester. The wear properties and coefficient of thermal expansion of the melt treated samples were determined using pin on disc wear testing machine and linear expansion measurement unit respectively. The results indicate that the Ni additions significantly enhanced the mechanical properties of the alloy, whereas, presence of Sr was detrimental. It was observed that the improvement in mechanical properties due to Ni was primarily due to refinement and transformation of the star shaped primary silicon into polyhedral crystals. However, the addition of Sr, both as separate and when combined with Ni, transformed the primary silicon into a faceted crystal and hence decreased the mechanical property. Among all, the Ni melt treated alloy samples showed lowest wear rate and coefficient of thermal expansion. Â© 2021 Elsevier Ltd. All rights reserved.
Effect of process variables on heat transfer and the product quality during layer deposition of Al4043 alloy by wire arc additive manufacturing
(John Wiley and Sons Inc, 2025) Raghavendra Pai, K.; Vijayan, V.; Samuel, A.; Prabhu, K.N.
In the present work, heat transfer dynamics between the substrate and the deposited metal is investigated to assess its effect on the evolution of defects and the quality of the product. A series of experiments involving the deposition of Al4043 wire were conducted on Al4043 aluminum alloy substrate at a voltage range of 13–19 V. A one-dimensional inverse computational model was adopted to estimate the heat flux transients. The metal/substrate interfacial heat flux was correlated with the microstructure evolution during the solidification of the metal. The experimental results clearly indicated that heat transfer plays a dominant role in the final finish and quality of the product and is controlled by variables, such as voltage, gas flow rate (GFR), wire feed rate (WFR), and forward traversal speed. At an integral heat flow (HF) in the range of 3000–5000 kJ/m2 corresponding to voltages between 13.8 and 14.5 V, argon GFR of 12–15 L/min, and a WFR of 4.1 mm/min, the porosity in the additively manufactured component was found to be minimum. The ultimate tensile strength was found to be 65 and 76 MPa, corresponding to the voltage of 13.5 and 14.5 V, respectively, and decreased to 25 MPa for a higher voltage of 19 V. At the GFR range of 8–10 L/min, the HF was in the range of 450–510 kJ/m2 with increased porosity (33%–42%). Porosity was found to decrease (15%–22%) with 12–15 L/min range of GFR and the corresponding HF was in the range of 700–950 kJ/m2. The specimens fabricated under these optimal parameters exhibited superior mechanical properties. © 2024 Wiley Periodicals LLC.
Effects of Phosphorus Treatment on Cooling Behavior, Heat Transfer, Microstructure, and Mechanical Properties of Hypereutectic Al-23%Si Alloy
(Springer, 2025) Vijayan, V.; Prabhu, K.N.
The influence of phosphorus (P) treatment on the microstructure, cooling behavior, interfacial heat flux, and mechanical properties of hypereutectic Al-23 Si alloy is investigated in the present work. Computer-aided cooling curve analysis revealed that higher cooling rates suppressed silicon cluster agglomeration and promoted nucleation of primary silicon at lower undercooling. The addition of P increased the nucleation temperature of primary silicon and resulted in finer silicon crystals. Eutectic silicon nucleation was facilitated by P treatment, with refined primary silicon acting as nucleation sites. Interfacial heat flux analysis demonstrated that P addition decreased the heat flux, attributed to the presence of less conductive primary silicon, and unmodified eutectic silicon microstructure. Microstructural analysis revealed the refinement of primary silicon and transformation of its morphology to polyhedral shape with P treatment. Heat treatment improved tensile properties, with refined primary silicon and copper precipitation contributing to enhanced strength. The morphology and composition of copper intermetallic varied with P and Cu content, influencing mechanical properties. These findings provide insights into optimizing alloy compositions and processing conditions for hypereutectic Al-Si alloys in various industrial applications. © ASM International 2023.
Enhancing mechanical properties of Ti-64 alloy through ECAE: lubricant optimization, microstructural evolution and optimal process parameters
(Springer-Verlag Italia s.r.l., 2025) Castelino, M.R.; Mallikappa, N.; Karinka, S.; Vijayan, V.; Shivananda Nayaka, H.S.; Valder, J.
This study explores the application of Equal Channel Angular Extrusion (ECAE) in enhancing the microstructural and mechanical properties of Ti-64 alloy. Finite Element (FE) analysis validates experimental outcomes, revealing a significant reduction in grain size, improved strength, and hardness. Microstructural analysis indicates dynamic recrystallization, transforming larger alpha (?) grains into smaller ones. Tensile testing demonstrates increased yield and ultimate strength in ECAE-treated specimens due to decreased grain size and heightened dislocation density. Lubricant optimization achieves low friction coefficients (0.02 and 0.04), reinforcing ECAE effectiveness. FE simulations and ANOVA analysis identify influential factors, leading to optimal parameter combinations. Isothermal ECAE successfully reduces grain size, resulting in substantial improvements in yield strength, ultimate strength, and hardness. These findings highlight ECAE's efficacy in enhancing the mechanical properties of Ti-64 alloy, with specific applications in biomaterials, particularly dental implants and bone support, as well as aerospace fasteners, where Ti-64 contributes to increased fuel efficiency, reduced emissions, and enhanced structural integrity. © The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature 2024.
Failures Investigation of Marine Propellers in Corrosive Environments
(Springer Nature, 2021) Mirashi, V.U.; Johnson, S.; Hegde, S.; Vijayan, V.; Cadambi, S.
Marine corrosion failure of fishing boat propellers made of cast Nickel Aluminium Bronze were investigated. Specimens extracted from the corroded propellers were characterized by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The alloy comprises several Fe3Al (κ1, κ2, κ4), NiAl (κ3) type intermetallic precipitates and β’ martensite embedded in Cu-rich α-matrix. Transverse sections of the corroded region showed two distinct zones; a non-uniform top oxide layer and a partially corroded zone with selective corrosion of the β’ martensite which run parallel to the κ3 precipitates. From the microstructural analysis it is adjudged that the aggressive local corrosion of the matrix is preceded by cracking of the oxide by erosion, cavitation, etc., A slow growth of the oxide layer follows that reduces the corrosion rate. However, the corrosion cycle repeats on erosion or cracking of the oxide layer when the propeller is used in marine waters. Coupon specimens immersed in actual marine conditions is presented that supports the above theory. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Heat Transfer and Deposition Strategies for Enhanced Mechanical Performance of Wire Arc Additively Manufactured SS316L Alloy
(Springer, 2025) Pai, K.R.; Vijayan, V.; Samuel, A.; Prabhu, K.N.
The work investigates the effect of various deposition strategies for wire arc additive manufacturing of SS316L on an SS304 substrate for industrial applications. Droplet deposition of SS316L on an SS304 substrate at varying current values (60–130 A) identifies the operational range for line deposition. The wettability, contact angle and spread area are evaluated along with heat flux transients for each current value. Heat flow calculated during line deposition at 90 A for horizontal and vertical substrates was 34297 kJ/m2 and 24137 kJ/m2 respectively. The corresponding values of porosity and micro-hardness indicate superior deposition at 90 A. Further investigation on deposition strategies such as interlayer current change with and without dwell time, deposition at 90 A with a dwell time of 30 s for five cycles, preheated substrates and Continuous Multi-Pass Deposition with 2 s is explored. Heat flux transients are computed for every deposition cycle using an inverse solver. Heat flow was found to be 63260 kJ/m2 and 58863 kJ/m2 for the 15th layer of interlayer current change of 90 ± 10 A and constant current of 90 A with dwell time respectively. By altering deposition parameters such as interlayer time gap and current the chromium content achieved through high-current density deposition significantly increased from 17.2% to 26% and 25.4% respectively. The ultimate tensile strength for the 80A sample without deposition strategies was found to be lower. Columnar grain morphology with dendritic structure was observed at higher currents. Finer equiaxed grains with lower interlayer fusion were observed at lower currents. Finer grain growth across the layers was achieved by adjusting the current between cycles in response to observed heat flux transients. EBSD analysis reveals the formation of brass texture with {110} in deposition strategies involving time gap and interlayer current change, indicating directional solidification thereby enhancing the overall mechanical performance of the as-deposited SS316L. © ASM International 2025.
Investigation of the effect of process parameters on porosity, microstructure and mechanical properties of Al–5 Mg alloy test samples fabricated by wire arc additive manufacturing
(Springer Science and Business Media Deutschland GmbH, 2025) Pai, K.R.; Vijayan, V.; Prabhu, K.N.
Wire arc additive manufacturing (WAAM) of aluminium alloy components has gained a lot of importance due to its ease of production of complex parts. However, its widespread acceptance as replacement for conventional manufacturing processes remains contested. The occurrence of defects, particularly porosity in products manufactured by WAAM remains a dominant reason for its lack of adoption. The gas flow rate, feed rate of wire, work piece and deposition voltage are some of the process parameters that affect the evolution of the porosity. The use of optimal process parameters is essential in obtaining defect-free aluminium products. In the present work, Al–5 Mg alloy was selected to investigate the role of WAAM process parameters on the product quality. The argon gas flow rates and wire feed rates were varied between 8–4 l/min and 3.6–4.7 mm/min, respectively. Melt deposition voltages were varied between 13 and 19.5 V. Microstructural studies using scanning electron microscopy and transmission electron microscopy were carried out to assess the effect of the process parameters on the quality of the product. The specimens were also subjected to mechanical testing. Microstructural analysis and mechanical testing results indicated that the optimal process parameters for producing defect-free products through wire arc additive manufacturing were a gas flow rate of 10 l/min, a wire feed rate of 4 m/min, and a deposition voltage of 14V. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.
Review of microstructure evolution in hypereutectic Al-Si alloys and its effect on wear properties
(2014) Vijayan, V.; Prabhu, K.
Al-Si alloys with silicon content more than 13 % are termed as hypereutectic alloys. In recent years, these alloys have drawn the attention of researchers due to their ability to replace cast iron parts in the transportation industry. The properties of the hypereutectic alloy are greatly dependent on the morphology, size and distribution of primary silicon crystals in the alloy. Mechanical properties of the hypereutectic Al-Si alloy can be improved by the simultaneous refinement and modification of the primary and eutectic silicon and by controlling the solidification parameters. In this paper, the effect of solidification rate and melt treatment on the evolution of microstructure in hypereutectic Al-Si alloys are reviewed. Different types of primary silicon morphology and the conditions for its nucleation and growth are explained. The paper discusses the effect of refinement/modification treatments on the microstructure and properties of the hypereutectic Al-Si alloy. The importance and effect of processing variables and phosphorus refinement on the silicon morphology and wear properties of the alloy is highlighted. © 2013 Indian Institute of Metals.