Transactions of The Indian Institute of Metals最新文献

In this study, a novel mixed stellite coating made from the 30% Stellite 3 and 70% Stellite 21 is deposited on H13 alloy using laser cladding technology, aiming at improving the micro-hardness and wear properties compared to Stellite 21. The microstructures of the mixed Stellite coating and Stellite 21 coating are examined using optical microscopy, scanning electron microscopy, and energy-dispersive spectrometer. The wear resistance of both Stellite coatings is evaluated by dry sliding wear test method. The results demonstrate that the Stellite 21 coating is composed of γ-Co, Co₃Mo interdendritic phase and M₂₃C₆ carbide, while the mixed Stellite coating is only composed of γ-Co and M₇C₃ carbide-enriched W and Mo. The mixed Stellite coating exhibits superior micro-hardness and wear properties compared to the Stellite 21 coating.

There is growing interest in biomedical applications of magnesium (Mg) and its nanocomposites due to their superior biodegradability, stiffness, and lower elastic modulus than other implant materials. However, the quick deterioration of magnesium alloys results in a rapid decline in mechanical properties, restricting their clinical application. Recent advancements, particularly in the integration of nanoparticle reinforcement, have enhanced mechanical strength while preserving the inherent toughness. These composites also show impressive corrosion resistance and compatibility with biological systems. However, uniformly dispersing nanoparticles as reinforcements within the Mg matrix and achieving the desired properties present significant challenges. Consequently, selecting appropriate magnesium nanocomposite production methods and identifying biodegradable, biocompatible, and osteogenic reinforcements are of utmost importance to overcome these obstacles and enhance mechanical, corrosion, and cytotoxic properties relevant to specific applications becomes imperative. This review investigates a range of fabrication techniques and types of reinforcement, analysing their impact on the mechanical properties, corrosion resistance, and biocompatibility of magnesium nanocomposites. Additionally, it investigates potential applications and proposes future research avenues for magnesium nanocomposites.

Utilizing mechanical alloying and hot compaction, we have successfully made high-entropy alloys (HEAs) with equiatomic proportions of Al, Co, Cr, Fe, and Mg, resulting in alloys demonstrating outstanding mechanical and tribological properties. This study comprehensively explored the impact of variations in phase evolution, density, microstructure, microhardness, and tribological and magnetic effects in the established AlCoCrFeMg HEAs. Field emission scanning electron microscopy (FE-SEM) was employed to examine microstructural changes, complemented by energy-dispersive spectroscopy. The FE-SEM micrographs revealed approximately 1.5% porosity, confirming densification of about 98.8% through Archimedes' principal, and X-ray diffraction identified a body-centered cubic solid solution phase. Furthermore, the melting point of the prepared high-entropy alloy was determined through differential scanning calorimetry. Assessing the mechanical robustness and tribological behavior, a Vickers microhardness tester and a ball-on-disk tribometer were employed for the sintered sample at 950 °C. With an 853.7 ± 20.27 HV_0.5 hardness and a coefficient of friction of 0.49, the developed HEAs exhibited remarkable magnetic properties, as verified by measurements using the physical property measurements system quantum design.

Comprehensive tests were carried out to study the effect of rotation speed and plunge depth on small diameter (5 mm) 2B06Al-T42/7B04Al-T74 refill friction stir spot welding joints. The cross section microstructures, the effective connection height (ECH), and the effective connection width (ECW) were characterized. In the meantime, the thermal mechanically affected zone/stir zone and the fracture path were also described. The lap joint’s hardness, shear strength, and failure mode were analyzed by optical microscope. It was found that the effective connection area (ECA = ECH × ECW) had a good correlation with the tensile shear property. At 1200 rpm, the plunge depth benefit improved the tensile shear strength of the welded joint, while at 1500 rpm, it had the opposite effect. The optimal welding parameters of 5 mm diameter joints were 2100 rpm of rotation speed and 1.0 mm of plunge depth, under those the tensile shear force of the joint was 3196.9 N. The shear-plug type fracture path was different at different rotational speeds. The fracture path of the welded joint at high rotational speed expanded from the stirring zone at 45° finally; while, the fracture path of the welded joint at low rotational speed fractured from the thermal–mechanical affected zone finally. The fracture path at high speed was more complex than at low speed.

To utilize the low grade iron ore resources of Karnataka, a banded hematite quartzite (BHQ) type ore was analyzed for its response to inert magnetization roasting followed by grinding and low intensity magnetic separation. Most gas-based reduction roasting techniques use CO and/or H₂ as reductant gases which require an appropriate setup to handle such hazardous gases. In the present work, a lab scale setup was used to perform magnetization roasting in an inert environment. The effect of holding time and temperature on magnetite formation was studied along with its response to beneficiation. The thermal decomposition route provides better control of reaction kinetics and forms no diamagnetic FeO leading to better upgradation and Fe recovery. Through this approach, the BHQ ore of grade 37.3 and 45.1% gangue was upgraded to a grade of 61% and 81% Fe recovery with > 95% magnetite conversion.

Friction Stir Welding (FSW) has become a trusted method for joining softer alloys like Aluminum and copper. However, for achieving improved joint efficiency and dissimilar joints, secondary heat sources are being used to make the materials softer to enhance the mixing through stirring. In this present work, a comparative study of multiple hybridization techniques to Friction Stir Welding was performed by utilizing two different energy sources viz. resistive heating through electric current and ultrasonic energy (UE). Different combinations of the hybridization studied for utilizing the multiple hybridization technique to the FSW process for improving the weld efficacy and defects-free weld even in case of dissimilar joints. A comparative study of the mechanical properties obtained by varying the process parameters have been performed. Three process parameters have been selected including UE (10 kHz), electric current (75–125 Amps), tool rotational speed (400–600 rpm), and tool transverse rate (30–50 mm/min). A significant improvement in the mechanical behavior has been monitored by adding electric current to the UAFSW by an in-house developed fixture. Similar optimistic results in the improvement of the property have been found by adding UE to EAFSW. A comparative study in the mechanical property has been presented to explain the improvement in the property. Microstructure study was also performed to analyze the behavior of Al–Cu joint.

Copper and titanium plates were used in the studies. These plates were joined together by explosive welding using different amounts of explosives. The resulting composite plates were heat-treated at different temperatures. In microstructural studies, it was observed that the joints with the least rate of explosive used had an almost flat joint interface and as the explosive rate increased, a wavy structure was formed. Hardness values were found to increase as the rate of explosives increased, but hardness values decreased after heat treatment. It was observed that notch impact strength decreased with increasing explosive rate, but there was an increase in impact toughness values after heat treatment. Torsional testing of all specimens revealed no visible defects. Neutral salt spray tests showed that the copper surfaces of the composite plates corroded, but there was no corrosion on the titanium side.

This study aimed to enhance the mechanical and microstructural properties of AA 7075-T6 aluminum alloy by incorporating zeolite powder using friction stir processing (FSP). The methodology involved preparing AA 7075-T6 plates with predrilled holes for zeolite powder insertion, followed by FSP with optimized parameters (650 rpm rotational speed and 12 mm/min traverse speed). Microstructural analysis was conducted using scanning electron microscopy, and mechanical properties were evaluated through tensile and hardness tests. The results demonstrated significant improvements in tensile strength, hardness, and elongation due to the fine grain structure and uniform distribution of zeolite particles in the weld Nugget zone. The optimized FSP parameters enhanced mechanical performance, making the zeolite-reinforced AA 7075-T6 alloy suitable for high-stress applications in aerospace and automotive industries. This study confirms the potential of zeolite reinforcement in improving the durability and reliability of aluminum alloys.

This investigation presents the development of third-generation advanced high-strength steels (AHSS) for automotive industries, focusing on materials with higher strength, plasticity, and crashworthiness. Three alloy steels Fe-6Mn-(1, 1.6, 2.0) Si were developed via a melting route using an arc melting furnace followed by homogenization at 1200 °C, hot rolling at 1100 °C, and then air cooling. The developed steels are characterized using FE-SEM, XRD, microhardness tester, and universal testing machine. The FE-SEM micrographs exhibit a complex phase microstructure containing pearlite, retained austenite, martensite, ferrite, and bainite. The microhardness values of novel alloys are measured as 423, 441, and 475 VHN. The tensile strengths of alloys were achieved at 1409 MPa, 1497 MPa, and 1438 MPa with elongations of 18, 15, and 14% respectively. Atom probe tomography results confirmed the presence of retained austenite of film thickness 25–27 nm. The fracture surface of alloy steel containing 1 wt% Si and 6 wt% Mn exhibits dimples, causing ductile fracture, while alloy steel containing 1.6–2.0 wt% Si and 6 wt% Mn combines dimples and facets, confirming intergranular fracture with a 14 % ductility limit. The average dimple size decreases from 0.82 µm to 0.64 µm with an increase in silicon from 1 wt% to 2 wt%.

This study investigates the impact of adding boron as a microalloying element to low silicon spring steel grades commonly used in automobile suspension systems. Boron enhances grain refinement, hardenability, strength, toughness, heat treatment response, and potentially corrosion resistance. Corrosion significantly affects suspension system lifespan in automotive applications due to environmental factors like dust and mud. A new spring steel grade with boron microalloying was developed at Visakhapatnam Steel Plant to improve mechanical and corrosion properties. The study examined conventionally produced spring steel grades subjected to quenching and tempering at different temperatures. Microstructural analysis was conducted using optical microscopy and SEM, while corrosion behavior was assessed in a 3.5 wt% NaCl environment through open-circuit potential and potentio-dynamic polarization tests. The study established that trace amounts of boron as a micro-alloying element in spring steel significantly influence both microstructural morphology and corrosion rate. The addition of boron increases the quantity of tempered martensite while reducing retained austenite and bainite, resulting in superior corrosion resistance in a 3.5 wt% NaCl environment. Oil quenching was found to be preferable over water quenching to prevent surface microcracks in both boron-added and non-boron spring steels.