Cast Structure Research Articles

Topology optimization based on combined mechanical analysis and variable density method for casting structure

In this study, a topology optimization method based on combined mechanical analysis and variable density is presented for a large-scale casting structure with complex thin-walled structures. First, the mechanical analysis model of the frame is established, the first-order bending and torsional modes and stiffness values of the all-cast aluminum frame are obtained, and the basic mechanical parameters such as bending/torsional mode and stiffness constraints needed for topology optimization are defined. Using the variable density method, unneeded material that can be removed from the casting structure is identified. According to the design requirements, the optimization objective function and constraint conditions are established, and the variable density method is used to solve the problem. Analysis of the mechanical results before and after topology optimization reveals that the modes and stiffness values are larger than the target values, and the mass of the frame is reduced by 10.2 kg (i.e. 13.9%) compared with the original design. The application of the combined mechanical analysis and variable density method to a casting structure can effectively achieve lightweight design.

Microstructure and Phase Composition of Novel Crossover Al-Zn-Mg-Cu-Zr-Y(Er) Alloys with Equal Zn/Mg/Cu Ratio and Cr Addition

The effect of 0.2%Cr addition on the structure, phase composition, and mechanical properties of the novel cast and wrought Al-2.5Zn-2.5Mg-2.5Cu-0.2Zr-Er(Y) alloys were investigated in detail. Chromium is distributed between primary crystals (5.7–6.8%) of the intermetallic phase and the aluminum solid solution (0.2%) (Al). The primary crystals contain for the main part Cr, Ti, Er(Y). The experimental phase composition is in good correlation with the thermodynamic computation data. The micron-sized solidification origin phases (Al8Cu4Er(or Y) and Mg2Si) and supersaturated (Al) with nano-sized Al3(Zr,Ti) and E (Al18Mg3Cr2) precipitates are presented in the microstructure of the novel alloys after solution treatment. The nucleation of η (MgZn2) (0.5%), S (Al2CuMg) (0.4%), and T (Al,Zn,Mg,Cu) (8.8%) phase precipitates at 180 °C, providing the achievement of a maximum hardness of 135 HV in the Al2.5Zn2.5Mg2.5CuYCr alloy. The corrosion potential of the novel alloy is similar to the Ecor of the referenced alloy, but the corrosion current density (0.68–0.98 µA/sm2) is still significantly lower due to the formation of E (Al18Mg3Cr2) precipitates and S phase precipitates of the aging origin, in addition to the T phase. The formation of E (Al18Mg3Cr2) precipitates under the solution treatment provides a lower proportion of recrystallized grains (2.5–5% vs. 22.4–25.1%) and higher hardness (110 HV vs. 85–95 HV) in the Cr-rich alloys compared to the referenced alloys. Solution treated, hot and cold rolled, recrystallized, water quenched and aged at 210 °C alloys demonstrate an excellent microstructure stability and tensile properties: YS = 299–300 MPa, UTS = 406–414 MPa, and El. = 9–12.3%.

Seismic-aseismic impact on marine depositional dynamics and sedimentary architecture: Study on multilayer-multiscale SSDS in Proterozoic Rohtas Limestone, India

The present study explores a diverse suite of soft-sediment deformation structures (SSDSs) preserved at multiple levels within the Mesoproterozoic carbonate succession of Rohtas Limestone in the Vindhyan Supergroup of India. The carbonate succession shows lithological heterogeneity, characterized by a sharp change of facies association and depositional environment. Three layers of SSDS, traced over 57 km, demarcate the lower lagoonal from upper open shelf deposits. Contorted laminae, load casts and flame structures, convolute laminae, ball and pillow structures, accordion folds and pillar structures within the limestone beds infer liquefaction-fluidization and plastic deformation. The lateral continuity, vertical repetition and confinement of SSDS beds at the interface of lagoon and open shelf deposits indicate the role of seismicity on facies succession. The SSDS beds show lateral variation in thickness and structures, depending on the distance from epicenter. The seismic trigger was accompanied by sudden deepening of the depositional environment and related marine transgression. The coarsening up packages within the lagoonal succession comprise load cast and flame structures, syn-sedimentary faults and intraclastic conglomerates. The open shelf succession shows several fining up cycles, with multiple load and flame structures with intraclastic conglomerate at the top. Origin of SSDS in association of the coarsening up sequence, and fining up cycle infers that intrabasinal tectonics and storms were the triggering agents for lagoon and open shelf successions respectively. The seismite in the studied succession not only reveals the seismicity during the Proterozoic, but also changed the sedimentary facies association, which may use as a diagnostic criterion for the identification of seismite. This study also highlights that seismic and aseismic impacts on sedimentary architecture and paleoceanography evolution.

Unveiling the Dualities: Exploring the Intersectionality of Caste and Gender in Meena Kandasamy's Literary Landscape

This research paper delves into the nuanced portrayal of caste intersectionality with gender in the literary works of Meena Kandasamy, a prominent contemporary Indian writer. Kandasamy's narratives provide a rich tapestry through which to examine the multifaceted experiences of individuals navigating the complex social structures of caste and gender in India. Through a close analysis of selected texts, this study aims to elucidate the ways in which caste and gender intersect to shape identities, power dynamics, and social hierarchies. Drawing on intersectional feminist theory and postcolonial perspectives, the paper explores how Kandasamy's characters negotiate and resist the oppressive forces of caste and patriarchy, while also highlighting the complexities and contradictions inherent in their struggles for agency and liberation. By engaging with Kandasamy's literature, this research contributes to a deeper understanding of the intricate interplay between caste and gender in contemporary Indian society, shedding light on the lived realities of marginalized individuals and communities.

Effect of the Fe/Mn Ratio on the Microstructural Evolution of the AA6063 Alloy with Homogenization Heat Treatment Interruption

The casting structure of the AA6063 alloy contains intermetallic particles of β-Al5FeSi, which can result in the fragility of the cast pieces. However, with heat treatment, the β phase transforms from a needle or plate form into an intermetallic phase known as α, which resembles Chinese-script in its morphology. To analyze the effect of the ratio of Fe/Mn with different ratios of 0.5, 0.75, and 1, a heat treatment process is used with intermittent interruptions. The alloy is subjected to a temperature of 575 °C for 12 h to determine the microstructural evolution of the β-Al6FeMn and α-Al15(FeMn)3Si2 phases. This study used scanning electron microscopy to conduct point analyses and elemental mappings of the intermetallics found in the casting and heat treatment samples. Additionally, X-ray diffraction was employed to determine the stoichiometry of the present phases. The results indicated that the cast structure contains β-Al6FeMn and α-Al15(FeMn)3Si2 phases and that the β-Al6FeMn phase transforms into the α-Al15(FeMn)3Si2 phase upon completion of the heat treatment process. By using specific Fe/Mn ratios, the formation of the needle-shaped Al5FeSi phase in the casting structure of the alloy can be inhibited, leading to the precipitation of phases such as β-Al6FeMn and α-Al15(FeMn)3Si2 instead.

Изучение влияния содержания гафния и эрбия на формирование микроструктуры при литье алюминиевого сплава 1590 в медный кокиль

Introduction. High-magnesium aluminum alloys are widely used in the automotive, building and aerospace industries due to its low specific gravity and high strength. The characteristics of such alloys can be improved by small additions of scandium and zirconium. However, scandium is very expensive, so in new generation alloys its amount is tended to be reduced. In the recently developed 1590 aluminum alloy, this was achieved by addition of erbium and hafnium. The objective of the paper is to study the effect of erbium and hafnium concentrations on the modification of the cast structure in 1590 aluminum alloy at high solidification rates. Research Methods. The paper investigates the microstructure, chemical composition and size of intermetallic compounds in specimens from ten alloy 1590 modifications with different hafnium and erbium contents cast into a copper chill mold with a solidification rate of 10 °C/sec. The grain structure was studied using an optical microscope. The chemical composition and size of the intermetallic phases were studied using a Tescan Vega 3 scanning electron microscope. Results and discussion. It is established that as the amount of hafnium and erbium increases, the cast structure is modified. In general, grain refinement with the addition of hafnium and erbium can be explained by a higher degree of supercooling between the solid and liquid phases. At a hafnium content of 0.16 %, the dendritic structure begins to transform into an equiaxed grain structure. This transformation can be explained by the appearance of primary intermetallic compounds of the Al3Sc type in the liquid phase. Such intermetallic compounds are identified at a concentration of erbium and hafnium equal to 0.16 %. Moreover, in all alloys eutectic intermetallic compounds are identified that contained manganese and iron and had no effect on the cast structure. Comparison with previously obtained results on the grain size of specimens cast into a steel mold shows that with higher solidification rate, the structure modification in 1590 alloy is getting less efficient. This is explained by an increase in the concentration of transition elements in the solid solution, primarily scandium, necessary for the formation of primary intermetallic particles.

CHANGES IN THE STRUCTURE AND PROPERTIES OF ALUMINIUM ALLOYS WHEN MODIFIED WITH POWDER COMPOSITIONS

Purpose. To determine the effect of modification with powder compositions on the structure and mechanical properties of cast and deformed aluminium alloys. Research methods. Metallographic analysis, stereometric metallography, testing of strength and plastic properties of cast alloys AL4, AL4C of the Al-Si system and deformed alloys 1545 of the Al-Mg-Sc system, 2219 of the Al-Cu-Mn system in their original and modified state. Results. Meltings of AL4, AL4C, 1545, 2219 alloys were carried out in the initial state and with melt treatment with a complex nano-disperse modifier of magnesium silicide Mg2Si and silicon carbide SiC with a particle size of 50...100 nm. The optimal content of Mg2Si+SiC (0.10%) for increasing σ0.2 of aluminium alloys was determined. A 1.6-fold reduction in the grain structure of cast alloys was achieved. The dependence of the particle size and the amount of the modifier on the mechanical properties of the alloys was established. In industrial experiments, the most effective particle size of Mg2Si+SiC was established for increasing σ0.2 of AL4, AL4C alloy from 115 to 260 MPa in the as-cast state. The increase in the strength properties of the modified alloys is 44 % compared to the original state. Scientific novelty. Further development, insight into the influence of melt modification on the parameters of the structure and properties of aluminium alloys was obtained. The use of nanodispersed complex modifier Mg2Si+SiС with a particle size of 50...100 nm is proposed. It has been confirmed that the use of complex nanodisperse modifiers allows you to actively influence the structure and mechanical properties of aluminium alloys. Practical value. It has been experimentally proven that the rational amount of the introduced complex modifier is 0.10% of the mass of the melt. A significant grinding of the grain structure and an increase in the strength properties of cast and deformed aluminium alloys were achieved as a result of the modification.

Using the radial shear rolling method for deep development of the cast structure of ingots of special materials

Using the radial shear rolling method for deep development of the cast structure of ingots of special materials

Determining the influence of technological parameters of electron beam surfacing process on the microstructure and microhardness of Ti-6Al-4V alloy

This paper reports the devised technology and equipment for manufacturing parts and assemblies with pre-defined properties by 3D printing methods. Underlying the technology is the application of a high-power electron beam to fuse metal powder in a vacuum chamber with the formation of successive layers that repeat the contours of the digital model of the product. The object of research is the process of surfacing products made of Ti6Al4V titanium alloy powder. The influence of technological parameters (speed and power of the electron beam) on the formation of the structure of the deposited metal and its mechanical properties was investigated. 3 samples printed under 3 modes were studied: beam speed, 270, 540, and 780 mm/s; power, 240, 495, and 675 W, respectively. The beam energy density was 44.5 J/mm3; the trajectory displacement step was 0.2 mm; the dynamic focusing current Idf was –0.31 A; and the powder layer thickness was 0.1 mm. The samples were examined by conventional methods. The structures were studied using an optical microscope, images were recorded with a camera. The Vickers hardness was measured with a microhardness meter in the direction from the technological supports to the surface of the sample, as well as along the surface of the product, and in the layers of the middle part of the sample. It was established that the articles had a dense cast structure of surfaced metal. On all samples, large crystallites with a uniform lamellar-acicular structure of α´-phase with a small amount of β-phase are formed along the height, mostly without defects with uniform microhardness both along the height and along the surface. It was determined that the surfacing mode at beam speed, 240 mm/s; power, 270 W is the most rational for practical use. Under this mode, a stronger structure is formed when it is crushed, reducing the width of the crystallites by 1.55 and 1.17 times compared to other modes

Influence of Melt Properties on the Dendritic Structure of Steel Castings

The paper presents the experimental results on the determination of melt parameters such as the energy of the boundary, contact angle, density and kinematic viscosity of low and medium alloy steels at different temperatures, as well as the dispersion of their dendritic structure in solidified castings. The analysis of the data obtained allowed revealing using mathematical models the influence of the chemical composition and temperature of melts on their properties and the dendritic structure of castings. It was established the variation of the melt parameters depending on the particular chemical elements of steels as C, Si, Mn, O, P, V, Cr. The established analytical dependences shown that increasing density and viscosity contributes to the dispersion of the dendritic structure and viscosity is of the major effect. The derived quantitative patterns allows to evaluate structure formation of cast structural low and medium alloy steels.

Thermokinetic Parameters of Solidification and Gradient Structure of Steel Castings

Thermokinetic Parameters of Solidification and Gradient Structure of Steel Castings

The Elasticity Of Caste In The Sikh Diaspora: Jat Cool and Caste Masculinities in the Pacific Northwest

Abstract: This article examines the transnational dimensions of caste and gender in the Punjabi Sikh diaspora of the Pacific Northwest. I explore how Jats (a landowning caste from Punjab, India) have positioned themselves at times as superior to Chamars (Punjabi Dalits or caste oppressed peoples) in the US-Canada borderland diaspora. Though Sikhism is a religion founded on anti-caste origins, the simultaneous repudiation of caste and celebration of Jat pride paradoxically illustrates structures of caste within the religion. The article unsettles the ways in which Jat men in the diaspora can be implicated in Jat pride and Jat cool: a social currency intertwined with popular culture and social media that reveals a particular caste masculinity. While not all Jats engage with Jat pride, and in fact many are involved in anti-caste praxis, it is important to situate the pervasiveness of these hierarchical ideologies within intra-Sikh communities to understand the permutations and stickiness of caste within the diaspora. I build on Asian American approaches to theorizing caste, youth cultures, and notions of “cool” to ultimately reveal how caste, rather than fixed or natural, is an elastic concept that is contingent upon how it is deployed within Sikh diasporic geographies and temporalities.

Socio-Cultural Dynamics of Cross-Border Labour Migration between Nepal and India

The enduring relationship between Nepal and India is the focus of this study, which delves into the social and cultural dynamics adopted by Nepali and Indian labour migrants in their respective destinations. The study extends to the examination of labour migrants' social backgrounds, encompassing aspects such as religion, caste, ethnicity, education, and family structure. Employing a mixed-methods approach, the study incorporates case studies supported by field observations in the destination countries. The gathered data undergoes analysis through descriptive statistics, allowing for a comparative assessment between the two migrant groups. While the socio-cultural status of both groups exhibits slight differences, disparities in caste and ethnicity indicators are noted between Nepal and India. Notably, a significant proportion of Nepali labour migrants hail from Dalit communities when compared to other caste and ethnic groups. In contrast, Indian labour migrants, predominantly from the Other Backward Class (OBC), exhibit a different trend. The volume of Nepali labour migrants heading to India surpasses that of Indian labour migrants to Nepal. The shorter migration distance for Indian labour migrants enables frequent visits to their place of origin, facilitating the celebration of local traditions and culture. In contrast, Nepali labour migrants encounter fewer opportunities to return to their destination regularly. A noteworthy observation is the comparatively higher educational status of Nepali labour migrants as opposed to their Indian counterparts heading to Nepal. The nuanced differences between the two migrant groups correlate with their religious affiliations and socio-economic backgrounds. Interestingly, both groups exhibit a limited number of enrolled children in destination schools, indicating a shared challenge in accessing education opportunities.

Strengthening aluminum matrix composite with additively manufactured 316L stainless steel lattice reinforcement: Processing methodology, mechanical performance and deformation mechanism

This study investigates various processing approaches, interface characteristics, and mechanical properties of an aluminum (Al) matrix composite reinforced with additively manufactured (AM) 316L stainless-steel (SS) lattice. The AM-316L-SS lattice, boasting a 30 % infill density, was fabricated using the laser powder bed fusion technique. The Al-matrix was integrated with the AM-316L-SS reinforcement through experimentation involving pre-stirring of the molten Al under pressurized and unpressurized die-casting conditions. A well-bonded interface, with cohesive regions, was obtained in the pre-stirred structures. In contrast, regions of decohesion were displayed in cast structures without pre-stirring, leading to the presence of pores and the manifestation of imperfect bond interfaces. Compression tests conducted on the sound composite demonstrated enhanced mechanical properties, with a compressive strength of approximately 163 MPa, significantly higher than that of the pure Al-matrix (approximately 80 MPa). Localized interface cracking was initiated by stress gradients and plastic deformation, leading to microcrack propagation into the Al-matrix.

Influence of Cast Structure Parameters on Ductility Properties of Low-Carbon Microalloyed Steels

Influence of Cast Structure Parameters on Ductility Properties of Low-Carbon Microalloyed Steels

ПЕРЕДУМОВИ ВПРОВАДЖЕННЯ 3D-ТЕХНОЛОГІЇ ДЛЯ ВИГОТОВЛЕННЯ МЕТАЛОВИРОБІВ ТА ПРИКЛАДИ ЇЇ ЗАСТОСУВАННЯ

A brief overview of modern additive manufacturing equipment, 3D technologies and leading companies in this field is provided. Such production for the modeling and optimization of casting structures and the production of metal products corresponds to the concept of Industry 4.0, aimed at obtaining competitive products quickly, conveniently, variably, with minimal personnel and the desire to exclude the subject from the technological cycle of production, close to the requirements of the consumer, including industrial and construction hardware. 3D technology, which includes the optimization of structures by digital methods, is an effective means of reducing the cost and weight of metal structures, reducing metal consumption. At the current transition stage to mass additive production, there is a need for a gradual combination of digital and traditional technologies in the process of industrial development on an innovative basis, which is an effective mechanism for overcoming the crisis phenomena of the war and post-war periods. In this regard, the use of 3D technology for obtaining cast metal structures, in particular those made by casting according to gasifying models, has significant opportunities. There are three examples of the application of 3D technology for printing metal structures, in the process of manufacturing lightweight openwork castings, which includes printing a foundry sand mold, and during 3D milling of a one-time foundry pattern from polystyrene foam. As one of the key drivers of Industry 4.0, 3D technologies, according to experts, are capable of standing on a par with traditional technologies, and in the near future, replacing at least half of the existing machine park and procurement equipment. There is a lot of talk about what is holding back the active use of 3D printers by enterprises, but the most common limitation is the unwillingness of the enterprises themselves to rethink, engineer their production, put it on the rails of digital technologies; certainly, it is difficult, but necessary to maintain their competitiveness.

Моделирование применимости метода радиальносдвиговой прокатки для закрытия дефектов литой структуры стального слитка

The aim of this work was to investigate the applicability of radial shear rolling method for deformation treatment of steel ingots containing cast structure defects. The radial-shift rolling (RSR) method is the most suitable for this purpose from the point of view of absence of restrictions on the billet length and realisable vortex flow of metal under conditions of favourable stress-strain state. An ingot with a diameter of 32 mm with an artificial transverse through defect was taken as the basic material. According to the results of the experiment, a 3D model of the final view of the defect cavity was built and the morphology of welding of its different zones was analysed. The volume of the defect was reduced from 620 mm3 to 380 mm3 . The experimental result showed that the RSR method is well suited for the closure of superficial defects with a depth of 1-3 mm. In the presence of axial defects, RSR method does not weld the defects, but stretches along the rolling direction changing the shape

Pseudo lamellae of Cu6Sn5 on the crystal facet of Sn in electrodeposited eutectic Sn-Cu lead-free solder

Eutectic Sn-Cu lead-free solder is developed using the pulse electrodeposition method from a citrate bath at different current densities like 0.1, 0.2, 0.4, and 0.5 A/cm2. The exact composition of all the deposits was confirmed through atomic absorption spectroscopy (AAS) analysis. The coating deposited at 0.2 A/cm2 constitutes 0.7 wt% of Cu which is similar to the eutectic Sn-Cu composition. Microstructural characterization was carried out with the help of a scanning electron microscope (SEM). Sn was the major constituent in all the deposits while a little amount of intermetallic i.e. Cu6Sn5 was present for the deposits at 0.1 and 0.2 A/ cm2. The energy dispersive spectroscopy (EDS) results showed traces of Cu6Sn5 in the deposits. The formation of Cu6Sn5 was also confirmed through X-ray diffraction (XRD). For the deposit at 0.2 A/cm2, the endothermic peak temperature in DSC is exactly the same as that of the melting point of Sn-Cu eutectic. This electrodeposited microstructure resembles the conventional eutectic Sn-Cu cast structure. The top view of the deposited Cu6Sn5 on the steps of Sn creates an illusion of lamellar structure. The effect of current density on the roughness was analyzed through AFM.

Mechanisms of modification of magnesium– manganese alloys

It is shown that the main modifying phases cannot serve as centers of crystallization of α‑phase microcrystals during solidification of magnesium‑manganese alloys.The superheating modification of these alloys is an adsorption‑nanostructural process. It is shown that adsorbed hydrogen acts as a modifying element of the structure of castings of magnesium‑manganese alloys. The mechanism of their modification by overheating consists of a significant decrease in the concentration of adsorbed hydrogen due to the predominance of its desorption processes from elementary magnesium and manganese nanocrystals in liquid magnesiummanganese alloys. The mechanism of modification of the main modifying phases of these alloys consists of a significant decrease in the concentration of adsorbed hydrogen in the melts through a significant decrease in the concentration of dissolved hydrogen.

Effect of Alloying Additives and Moulding Technology on Microstructure, Tightness, and Mechanical Properties of CuSn10 Bronze.

Thise research was conducted to determine the impact of the applied casting technology, mould and alloying additives on the tightness of the CuSn10 cast alloy. Under industrial conditions, a series of experimental melts were made that were characterised by varying the concentrations of the main alloying element (Sn) and the introduced alloying additives (Si, Zn, Zr). The mould was made from green sand and used the CO2 moulding process. To assess the influence of the alloying additives, a metallographic analysis of the studied alloy was carried out, and the alloy's microstructure was examined using optical and scanning electron microscopy. The introduced alloying additives affected the properties and microstructure of the studied alloy. As alloying additives, zirconium resulted in a visible refinement of the microstructure, while silicon improved the fluidity and quality of the casting's external surface. The use of alloying additives and moulds made using different technologies is intended to improve the structure of the tin bronze castings produced and to find the best solution to significantly eliminate the lack of leakage of the castings. The castings were subjected to mechanical processing, and a leak test was performed using the pressure drop method. The conducted research allowed us to determine which technology, applied to production, will bring about a reduction in the problem and will inform further investigations.