Browsing by Author "Sinhmar, Sunil"

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Art of friction stir welding to produce weld joint without rotation of shoulder with narrow heat-affected zone and high corrosion resistance
(Sage, 2020-08) Sinhmar, Sunil
This present study uses an indigenously designed non-rotating shoulder friction stir welding (NRSFSW) tool to weld AA2014 aluminium alloy. This tool is harnessed with a penetrated material removal mechanism. Generally, the heat-affected zone (HAZ) is the most severely affected region in the conventional FSW (CFSW) joint of heat-treatable aluminium alloys. The prime novelty of this work is to reduce the width of most corrosion susceptible region of the FSW joint using a non-rotating shoulder tool. The corrosion behaviour of the NRSFSW joint has been investigated and compared to the CFSW joint. The NRSFSW tool resulted in focused heat input which eventually reduced the width of the HAZ and improved corrosion resistance as compared to the CFSW tool.
Controlled Oxide Deposition Improves Mechanical and Biomedical Applications of Titanium Alloy
(Springer, 2024-01) Sinhmar, Sunil
This chapter explicates information about surface modification techniques to enhance mechanical engineering as well as biomedical engineering applications of titanium and its alloys. Ti6Al4V has some valuable properties like a high strength to weight ratio, high bone cell attachment bone cell proliferation etc., which differentiates it from other materials and alloys. Furthermore, to make it highly reliable for long-term service various additive manufacturing techniques such as anodic oxidation and thermal oxidations are frequently used to improve aesthetical appearance generally utilized in architectural engineering and osseointegration property utilized in medical engineering, etc. Electrolytic concentration, solution temperature, time span, anodic voltage and current density are controlled parameters of the anodization process. 0.5 M sulfuric acid with 10% HF at anodic voltage of 40 V formulates homogeneous nanoporous oxide film of uniform thickness over titanium substrate. Anodization offers high surface hardness as compared to untreated one, almost six times improvement in surface hardness has been observed. Homogeneous nanoporous oxide film facilitates improved bone cell attachment, cell proliferation and osseointegration properties.
Effect of variation in power input on dissimilar materials (Cu-Al) laser welding for battery manufacturing
(Elsevier, 2024-06) Sinhmar, Sunil
Battery manufacturing inherently requires the joining of dissimilar materials. The performance of a joint is significantly derived from the joining technique as well as the process parameters, which, in turn, determine the life of the product. The current study discusses the efficacy of laser welding to develop dissimilar joints of thin sheets of Al and Cu for battery applications at varying power inputs. Thin sheets of aluminium and copper were welded using laser power inputs of 2.0 kW, 2.1 kW, and 2.2 kW. A power input of 2.1 kW results in 86 % higher weld penetration than the 2.0 kW. High power input results in through-thickness penetration, which drastically affects the mechanical strength of the joint. A weld joint developed at 2.1 kW shows a higher shear load of 800 N among all the power input parameters. An intermetallic layer forms at the weld interface for all three power inputs. However, the width of the intermetallic layer increases with the laser power input.
Effect of weld profile geometry on dissimilar laser welded joints for battery applications
(Springer, 2025-10) Sinhmar, Sunil
A transition from fossil fuels to greener technologies like batteries is essential for a sustainable future. This study explores the impact of weld profile geometry on laser-welded aluminum–copper (Al–Cu) dissimilar lap joints at a constant power input of 2.1 kW, relevant for bus-bar connections in electric vehicle battery manufacturing. Two weld profiles: parallel line and circular, were compared in terms of microstructure, mechanical strength, electrical resistance, and corrosion behavior of the joints. Microstructural analysis showed that the circular weld exhibited deeper penetration and a wider Al2Cu intermetallic layer, while the parallel profile had a thinner, sharper, and uniform interface. Mechanical tests indicated that the circular profile achieved 66% higher peak load and better ductility. It also showed lower electrical resistance and reduced temperature rise under currents of 50 A, 100 A, and 150 A, suggesting improved conductivity than parallel line weld. However, electrochemical testing revealed higher corrosion current density and severe interfacial degradation in the circular profile due to its broader, uneven intermetallic zone. The findings emphasize that weld profile geometry significantly influences joint behavior, and optimized weld design can enhance performance without increasing power input, particularly relevant for battery interconnects and lightweight electronic applications.
Effect of weld thermal cycle on metallurgical and corrosion behavior of friction stir weld joint of AA2014 aluminium alloy
(Elsevier, 2019-01) Sinhmar, Sunil
Friction stir welding of AA2014 aluminium alloy was performed at seven different speed combinations. Weld thermal cycles were measured at all the speed parameters and corresponding peak temperatures were observed at higher tool rotation speed and lower welding speed. Hardness and tensile tests were performed to study the mechanical properties of the weld joints. Corrosion behavior was studied using immersion, Tafel and electrochemical impedance spectroscopy tests. Optical microscopy, FESEM, XRD and transmission electron microscopy were used to investigate the metallurgical behavior of the weld joints. Microhardness and corrosion resistance were found higher at low rotation speed and high traverse speed. Corrosion behavior has been discussed in light of microstructure.
Enhancement of mechanical properties and corrosion resistance of friction stir welded joint of AA2014 using water cooling
(Elsevier, 2017-01) Sinhmar, Sunil
An investigation on the microstructure, mechanical properties, and corrosion behavior of friction stir welded joint of AA2014 in natural cooled (NC) and water cooled (WC) conditions have been reported. Optical microscopy, field emission scanning electron microscopy (FESEM) with Energy dispersive X-ray spectroscopy (EDS), Vicker's microhardness, tensile testing, X-ray diffraction (XRD), and electrochemical potentiodynamic polarization corrosion test (Tafel curve) were carried out to characterize the friction stir weld joints in both the cooling conditions. Water cooling resulted in higher strength and microhardness of friction stir weld joint compared to the natural cooling. The width of heat affected zone was reduced by the use of water cooling during friction stir welding (FSW) and minimum hardness zone was shifted towards weld center. The corrosion test was performed in 3.5% NaCl solution. Corrosion resistance of water cooled joint was found higher than natural cooled FSW joint. The precipitation behavior of weld nugget and heat affected zone impacts the corrosion resistance of FSW joint of AA 2014. Hardness, tensile, and corrosion properties of FSW joints produced under NC and WC conditions have been discussed in the light of microstructure.
Enhancement of the Mechanical and Corrosion Behaviour of FSW Joints Using a Novel Particle Reinforcement Approach
(Springer, 2024-01) Sinhmar, Sunil
Reinforcement of external particles during friction-stir welding (FSW) is significantly used to improve the weld joint’s performance. The present study involves reinforcement of the external particles in the weld joint without the aid of grooving or drilling. The FSW joint of AA2014 aluminium alloy has been reinforced with boron carbide (B4C) powder particles. The performance of the joint was investigated in terms of mechanical behaviour using tensile and microhardness tests as well as corrosion (electrochemical) behaviour using immersion, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) tests. The presence of boron carbide particles in the joint improves the tensile strength, microhardness, and corrosion resistance. In light of the microstructure, the impact of the reinforcement of these particles on the weld joint performance has been thoroughly discussed.
Friction Stir Processing of AA 7039 Alloy
(2014-12) Sinhmar, Sunil
Friction stir processing (FSP) is an effective solid state surface modification technique used to improve the surface properties of metals like aluminium, and titanium controlled structural refinement. In present work, friction stir processing of 5 mm thick plate of Al-Zn-Mg alloy (AA 7039) was carried out using a conical pin and overlap of 50%. Modified surfaces were characterized in respect of macrostructure, microstructure, hardness and tensile properties. It was observed that friction stir processing refined the microstructure of AA 7039 alloy and increased the ductility (%elongation). However, tensile strength and hardness were found to be adversely affected. Hardness has been found to be increased with number of passes during friction stir processing.
Friction Stir Welding
(CRC Press, 2024) Sinhmar, Sunil
This chapter deals with the various aspects of joining dissimilar materials using the friction stir welding (FSW) technique. The joining of dissimilar materials is an important need for the manufacturing sector, especially the automobile industry. It helps in the weight reduction of the vehicle, which in turn reduces fuel consumption. Therefore, dissimilar weld joints are important from both an economical and sustainable point of view. FSW develops the joint below the melting point of the base metal, thus significantly reducing the chance of intermetallic formation, especially in the case of dissimilar friction stir-welded joints. FSW is widely used for the joining of aluminum alloys. The automobile industry commonly uses the dissimilar joint of aluminum alloys with other metal systems, like steel, to achieve a high strength-to-weight ratio. In view of this, the characteristics of FSW joints of dissimilar aluminum alloys, aluminum to other metal systems, and dissimilar metal systems other than aluminum, as well as major issues with the dissimilar FSW joints, are discussed. The metallurgical, mechanical, and electrochemical behaviors of the dissimilar FSW joints are discussed and correlated with the change in microstructure.
Influence of a Stationary Shoulder Friction Stir Welding Tool on the Mechanical and Corrosion Properties of AA2024 Aluminum Alloy Joints at Different Parameter Values
(Springer, 2023-11) Sinhmar, Sunil
Sound weld joints of similar AA2024 aluminum alloy plates of 6 mm were achieved unprecedentedly at different rotational (386-1216 rpm) and traverse speeds (13-90 mm/min) using an indigenously developed stationary shoulder friction stir welding (SSFSW) tool. Results indicate a smooth and bowl-shaped symmetrical nugget zone (NZ) with fine equiaxed grains. The grains as well as the nugget zone width vary with the speed variation. A change of 16% in the width of NZ is observed with an increase in traverse speed from 13 to 90 mm/min. The SSFSW tool reduces the width of the weakest region of the weld joint, known as the heat-affected zone, by almost 50%. The SSFSW joint produced at 931-90 mm/min shows the highest value (101 HV) of the minimum hardness region as compared to other parameters. The SSFSW tool shifts the weakest region toward the NZ, as substantiated by the fracture location of the tensile samples. In addition, SSFSW joints show higher corrosion resistance in NZ due to recrystallized fine grains as compared to HAZ. The SSFSW tool reduces the width of the most severely corrosion-affected region and, hence, improves the corrosion resistance of the joint.
Investigation of corrosion and electrical resistance in laser welded Al-Cu joints for EV batteries
(Elsevier, 2024-12) Sinhmar, Sunil
This study investigates the correlation among the microstructure, electrochemical, and electrical properties of laser-welded Alsingle bondCu joints used in battery applications. Aluminium and copper thin sheets were laser welded at three power inputs (2000 W, 2100 W, and 2200 W), and joints were evaluated for their macro- and microstructural features, corrosion behaviour, electrical resistance, and temperature rise during current supply. Results indicated that higher power inputs led to deeper weld penetration and increased intermetallic formation, impacting corrosion resistance and electrical characteristics. Electrochemical impedance spectroscopy (EIS), immersion, and Tafel tests confirmed that joints welded at 2200 W exhibited superior corrosion resistance than others, and this was attributed to a uniformly mixed Alsingle bondCu region. The electric characteristics of the joints were assessed by supplying electric currents of 100 A, 150 A, and 200 A. In comparison to a weld joint developed at 2000 W, the electrical resistance of weld joints developed at 2200 W increased by 44.5 %, 37.87 %, and 39.31 % at 100 A, 150 A, and 200 A current supplies, respectively. Electrical resistance measurements revealed a direct correlation with weld quality and temperature rise, with implications on battery performance. These findings underscore the critical role of joint quality in optimizing battery performance.
Investigation of mechanical and corrosion behavior of friction stir weld joint of aluminium alloy
(Elsevier, 2019) Sinhmar, Sunil
Friction stir welding of AA2014 aluminium alloy was performed at 931 rpm and 41 mm/min speed. Weld joint properties were compared with the base metal. Optical microstructure and FESEM analysis with energy dispersive spectroscopy (EDS) were performed. Microhardness and tensile tests were performed to study the mechanical behavior of base metal and FSW joint. Direct current based corrosion test was carried out to study the corrosion behavior. Mechanical performance of AA2014 was reduced after the welding. Corrosion resistance of the weld joint was higher than the base metal. Presence of precipitates affected the performance of base metal and weld joint.
Machine learning-assisted wire arc additive manufacturing and heat input effect on mechanical and corrosion behaviour of 316 L stainless steels
(Elsevier, 2024-10) Sinhmar, Sunil
Predicting the track forming factor or height-to-width ratio (H/W) in wire arc additive manufacturing is crucial for optimal path planning, heat distribution, structural integrity, distortion control, process efficiency, and defect prevention, ensuring high-quality and reliable components. Different analytical and numerical modeling methods have been introduced to predict the H/W ratio. However, the accuracy of these predictions is relatively low due to the challenges associated with handling complex and non-linear regression equations. This study addressed the challenges by implementing data-driven predictive modeling to predict the H/W ratio from the input process parameters. A stacking ensemble learning approach is employed, where a meta-model integrates predictions from multiple base learners to enhance overall performance. The model performance was evaluated by Coefficient of determination (R2), mean squared error (MSE), and mean absolute error (MAE). The model was validated by comparing the experimental and predicted values based on which five thin walls are printed with different heat inputs. The study also explores the impact of heat input on microstructure, mechanical, and corrosion properties. The findings indicate that a significantly low heat input (178 J/mm) and higher heat inputs (> 356 J/mm) decrease the wire utilization. With increasing heat input, ferrite content increases, microstructures become coarser, dendritic spacing increases, and ferrite transitions from lathy to skeletal. Further, lower heat input (235 J/mm) reduces δ-ferrite, suppresses atomic segregation, and increases Cr and Mo in the matrix. YS and UTS decrease with higher heat inputs, anisotropy decreases, and Vickers microhardness drops from 228 (178 J/mm) to 194 Hv (586 J/mm). Additionally, the corrosion resistance deteriorates with increasing heat input, as evidenced by higher pitting potential (Epit: 0.389 V vs. 0.368 V vs. −0.023 V) and lower corrosion current density (Icorr: 6.76 ×10−7 A/cm2 vs. 7.946 ×10−7 A/cm2 vs. 8.91 ×10−7 A/cm2) for heat inputs of 235 J/mm, 281 J/mm, and 356 J/mm, respectively.
Mechanical and Corrosion Behavior of Pure Aluminium Added Friction Stir Weld Joint of Aluminium Alloy
(Trans Tech Publications Ltd., 2019-09) Sinhmar, Sunil
Friction stir welding (FSW) of AA2014 aluminium alloy was performed by sandwiching pure aluminium (Al) in the form of strip between the abutting surfaces. Mechanical and corrosion behavior of weld joint with and without pure aluminium addition was compared. Friction stir welding was carried out at rotational speed of 931 rpm and traverse speed of 41 mm/min. Pure aluminium strip of 1 mm thickness was used for incorporating Al in weld nugget zone. Microstructure analysis was carried out using optical microscope and FESEM with energy dispersive spectroscopy (EDS). Microhardness and tensile testing were performed on the weld joints. Corrosion behavior was investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (Tafel) test. FESEM analysis was performed before and after corrosion test. Traces of pure aluminium strip were observed in the microstructure. The incorporated strip was found not to be uniformly distributed in the nugget zone. Pure aluminium addition reduced the extent of formation of the second phase particle in the nugget zone as compared to the normal FSW joint i.e. without Al addition. This metallurgical homogeneity resulted in better corrosion resistance of the Al added weld joint than the normal FSW joint.
Mechanical behavior of FSW joint welded by a novel designed stationary shoulder tool
(Elsevier, 2020-03) Sinhmar, Sunil
A novel stationary shoulder friction stir welding (SSFSW) tool was developed with provision for automatic removal of plasticized material entering into the shoulder during the welding. Main objective of this tool design was to obtain a symmetrical weld joint with narrow heat affected zone. Mechanical and metallurgical properties of AA2014 aluminium alloy SSFSW joint were compared with the conventional FSW joint. Sound weld joint with enhanced mechanical properties were obtained by the stationary shoulder tool. Optical microscopy, FESEM analysis along with EDS, transmission electron microscopy, XRD analysis, microhardness and toughness test were performed on both types of weld joint. Weld thermal cycle and heat generation were analyzed for stationary shoulder and conventional FSW tool and it was found that the SSFSW tool shoulder generates lesser heat than conventional FSW tool.
A study on corrosion behavior of friction stir welded and tungsten inert gas welded AA2014 aluminium alloy
(Elsevier, 2018-04) Sinhmar, Sunil
The present study comprises the comparison of the electrochemical behavior of friction stir weld (FSW) joint and tungsten inert gas (TIG) weld joint of AA2014 using immersion test, potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). Weld thermal cycles and microhardness were correlated with corrosion behavior of the weld joints. TIG weld joint showed lower corrosion resistance than FSW joint. Heat affected zone was the most corrosion susceptible region in both type of weld joints. Optical microscopy, FESEM, TEM and XRD analysis were performed to discuss the corrosion behavior in light of the microstructure.