Cast Structure Research Articles

Using the Radial-Shear Rolling Method for Casted Zirconium Alloy Ingot Structure Improvement

In developing materials for the nuclear industry, it is crucial to enhance both alloy composition and processing methods. This study focuses on investigations of applying radial-shear rolling (RSR) to a Zr-1%Nb alloy ingot, aiming to refine its microstructure and improve its properties for nuclear applications. This method, with complex vortex metal flow inside of a casted workpiece, has not been previously tested for processing zirconium ingots, so experimental verification of its applicability is of scientific interest. The 30 mm diameter ingot, produced by vacuum induction melting, was initially rolled to 20 mm at 800 °C to eliminate defects and refine the cast structure. A second rolling stage reduced the diameter to 13 mm at 530 °C, resulting in an ultrafine-grained structure. The RSR method effectively combines structural refinement and defect healing within fewer cycles, making it suitable for producing components for nuclear reactors. This approach demonstrates a potential reduction in traditional processing steps, providing a more efficient route for preparing high-quality materials for nuclear applications.

Control and optimization of defects in die casting of complicated right crankcase cover

The die-casting process of ADC12 aluminum alloy right crankcase cover was simulated based on AnyCasting software, and the influence of pouring temperature, initial mold temperature and injection speed on the filling and solidification process of ADC12 right crankcase cover casting was explored by orthogonal experiment method. The optimal process parameters were obtained through optimization, and the die-casting mold was designed. The program was verified in production. The results show that the porosity and shrinkage of the right crankcase cover are mainly concentrated in the thick wall part. The sequence of process parameters that affect the residual melt modulus is pouring temperature, initial mold temperature, and injection speed; The best combination of process parameters: pouring temperature is ∼680 °C, initial mold temperature is ∼200 °C, injection speed is ∼5 m/s. By analyzing the filling process and temperature field simulation results, the casting structure, mold structure and cooling system were optimized, and the process plan was improved. The production verification was carried out according to the optimized process plan. The casting quality is good and has no obvious defects, which meets the actual production needs.

On the reliability of steel frame joints in earthquake zones exposed to low temperatures

The paper analyzes the existing construction solutions of steel frames with a box-section column and an I-beam crossbar in order to use them in earthquake zones, including areas with low temperatures. Such solutions will allow the structure to accept the seismic inertial forces, while maintaining its bearing capacity throughout the entire period of operation. In order to solve this problem, the study proposes to use steel frame joints, which can be used both for the entire frame of the building and on individual floors, thereby creating a “flexible story” effect. The authors studied articles, books and patents issued in Russia, the United States, Japan, China and Iran, analyzed the factors that reduce the reliability and performance characteristics of the joints. The main factor consists in a welded joint, which is used to attach the crossbars to the columns, transverse ribs in the column body, and to form the box section of the column from sheets, angles or channels. The reliability of the welded joint is reduced even more under conditions of seismic zones with low temperatures in Russia. However, units without welded joints require special cast parts or structures, thereby reducing their availability. In this regard, the task consists in developing new original construction solutions for joints that meet the requirements of reliability and availability.

Development of Cellular Cast Structures for Improving Heat Transfer in Thermal Energy Storage Systems

Development of Cellular Cast Structures for Improving Heat Transfer in Thermal Energy Storage Systems

Public health as critique: examining the caste of filth and disease in Katherine Mayo’s Mother India

Drawing on Dalit writer Kanwal Bharti’s 2019 translation of Katherine Mayo’s Mother India (1927), this essay argues that through the employment of a radical anti-caste reading practice, the original text yields a powerful critique of Hindu caste structures and Hindu supremacist ideologies that assume a new significance in contemporary India. An against-the-grain reading of Mayo’s emphasis on life and health as opposed to casteized purity, when unmoored from the author’s original intentions, offers a vision of public health that operates in conjunction with the social, and can be reclaimed to the advantage of the marginalized and dispossessed. In its emphasis on the impact of colonial modernity on marginalized lives in colonial India, the text finds an intriguing alignment with radical anti-caste politics. This solidarity between what is widely recognized as a colonialist critique on the one hand, and radical anti-caste thought on the other, I argue, is a reminder of the uneasy relationship between colonial politics, Hindu nationalism, and anti-caste politics that sought to use colonial rule to strategically counter Hindu supremacy.

A comparative study of the microstructure and shape memory behaviour of NiTi, NiTiHf, and Pt-added NiTiHf alloys

The microstructure, substructure, transformation temperature, and recovery ratio of a novel Ni45Pt 5 Ti30Hf20 alloy are reported in the current work. The properties of binary TiNi and ternary TiNiHf alloys are also characterized to establish a comparative basis for shape memory behaviour. The microstructure of the cast structure of Ni45Pt5Ti30Hf20 alloy showed a dendritic matrix and interdendritic eutectic-like mixture, and that of the homogenized structure consisted of martensitic matrix and secondary phase of dark contrast having the composition (Ti+Hf)2(Ni+Pt). Pt substitution of Ni in the ternary alloy with 20 at.% Hf by 5 at.% leads to a decrease in the Af, As, Ms, and Mf . Ms and Mf represent the temperatures at which austenite to martensite transformation starts and completes, respectively, while As and Af represent the temperatures at which martensite to austenite transformation starts and completes, respectively. The XRD studies showed that the structure of martensite is B19′ and TEM studies showed that the substructure of martensite in Pt modified NiTiHf alloy is similar to that of ternary NiTiHf alloy. The shape memory recovery of the Pt-modified alloy is similar to the ternary alloy at higher strength levels. The recovery ratio determined using Vickers indentation is compared with that determined using compression tests to provide an efficacy of small volume tests for screening of these alloys.

A novel nonlinear pressurization method for counter-gravity casting of cross-sectional mutation structures

In order to ensure the filling integrity of complex counter-gravity casting and improve metallurgical quality, it is necessary to shorten the filling time while avoiding air entrainments. To address this contradiction, a novel nonlinear pressurization method was proposed in this study. Through systematically analyzing the relationship between critical gating velocity and stable filling height, a criterion for iterative calculation of nonlinear pressurization curve was established, and an empirical expression between nonlinear pressurizing speed and the filling height was obtained. Based on the empirical expression, a nonlinear pressurization curve can be designed according to the casting structures and initial pressurizing speeds. The above nonlinear pressure curve design method was validated through water filling experiments. It was proved that the nonlinear pressure curve can shorten the filling time while avoiding air entrainments. It provides important processing control method for improving the low-pressure casting performance of complex castings.

Static and dynamic analyses and multi-objective optimization of wafer thinning machine’s design variables

In order to meeting the physical strength, heat dissipation and dimensional requirements of chips, the wafer surface needs to be thinned by wafer thinning machines. In the design of wafer thinning machine, the analysis and optimization of castings is an important and complex issue. In this study, the multi-objective optimization of wafer thinning machine’ s design variables are executed due to static and dynamic analyses. According to the analysis results, the design quality, amplitude and equivalent stress of the casting are optimized. The inner diameter of the ring, the height of the ring, the height of the middle groove, and the height of the groove on both sides are selected as the main design variables of the optimization. The results show that the static deformation of the optimized cast structure is 8% lower than the original structure, the overall mass is 4% lower, the operating frequency is 3.5% lower, higher stability, smaller mass and amplitude are obtained after optimization. The research has a great significance for the wafer thinning machines design, and provides theoretical guidance for the development of other lithography equipments.

Influence of Noble Metals on Morphology and Topology of Structural Elements in Magnesium Alloy.

The main motivation for this study was to improve implant materials. The influence of silver and gold on the structure and mechanical properties of Mg-Nd-Zr alloy was studied. In the work, quantitative and qualitative evaluation of the structural components of magnesium alloy with noble metal additives was performed. The research methods used were investigation of the mechanical properties and observation of micro- and macrostructures. The results showed that modification of magnesium alloy with Ag and Au contributes to the formation of spherical intermetallics of smaller size groups, which become additional centers of crystallization and grind the cast structure. The best composition from additional alloying with silver and gold was determined. Their positive effect on the strength and ductility properties of the metal was established. Preclinical and clinical testing was performed and the prospects for noble metal modification of bioabsorbable magnesium alloy for implant production usage were shown.

Examinations on small bronze items from the Hallstatt period burial ground at Mitterkirchen in Upper Austria

Abstract A partially destroyed burial ground from the Hallstatt period in the area of Mitterkirchen in Upper Austria was archaeologically investigated. The graves are dated to the Hallstatt C period corresponding to the 8th/7th century BC. Two triangular-headed nails and two lamellar “Buckel” (domed bronze plates) made of Sn-bronze were available for material investigations. One of each was subjected to metallographic examinations. The triangular-headed nail’s bronze contains about 15 wt. %Sn. The dendritic cast structure and the eutectoid phase Cu41Sn11 are clearly visible. What is noticeable is that a Cu41Sn11 layer formed in some areas of the surface. The lamellar Buckel’s microstructure is recrystallized and exhibits only a few deformation twins. Its bronze contains about 13 wt. %Sn. Hence, only very little Cu41Sn11 is present. Elongated Cu2S precipitates indicate that the initial sheet was manufactured by fine forging.

Computational Investigation of the Influencing Parameters on the Solidification of Thermoplastic Beryllium Oxide Slurry in a Cylindrical Shell

This article presents a computational study of the influencing parameters on the solidification of the thermoplastic beryllium oxide slurry in an annular forming cavity. The main purpose of this paper is to study the effect of cooling and casting conditions on the solidification of the BeO suspension by considering the temperature-dependent rheological and physical properties. The results of calculations of the Bingham–Papanastasiou rheological model with experimental data in the intervals of phase transitions with different casting rates of beryllium ceramics have been validated. The use of the regularization parameter made it possible to approximate the flow of the slurry at all levels of its shear rates as highly viscous, followed by a continuous transition to a solid state. The speed of heat removal from the molding during the solidification period is determined by the speed of movement of the slurry and the temperature field on which the width of the transition region depends. The process of solidification of the slurry mass has been evaluated by changing its heat flow distribution and density along the length of the concentric channel. The obtained model calculation results make it possible to control the casting process and eventually realize a uniform structure of castings.

Методика дослідження зародження кристалів у розплавах краплинним методом

The purpose of this work is to develop scientifically based ways of influencing the process of nucleation of crystallization centers in metal melts to control the formation of the cast structure and the properties of their blanks at the first stage of metal product production (at the casting stage). The possibility of controlling the nucleation of crystals in their melts was studied on transparent model environment (paraffin and salol) using the drop method, and the dependence of the crystallization kinetics of droplets with a dispersion of 100÷200 μm on their overheating temperature, the duration of exposure in an overheated state, and the degree of supercooling was established. Physical modeling on transparent environment made it possible to display images on a laptop screen with the help of a digital camera mounted on a microscope and to observe the nucleation and growth of crystals in real time, to determine the duration of solidification of all observed drops, depending on the experimental conditions. The criteria for evaluating the crystallization process of the investigated environment were the curves of the crystallization kinetics of drops from their melts. The nature of the change in the crystallization kinetics curves of the experimental environment, in our opinion, confirms the assumption about the decisive role of impurities in the crystallization processes of any alloys. The logical confirmation of the hypothesis about the decisive role of impurities in the processes of crystallization from the same positions of heterogeneous nucleation is the dependence of the number of solidified drops of experimental environment of the same diameter on the degree and duration of their overheating. It is likely that with greater overheating of the melt (or longer exposure to this overheating), partial deactivation (dissolution) of the impurities present occurs and the number of solidifying drops changes for the same supercooling. The analysis of the obtained results indicates a heterogeneous mechanism of crystal nucleation even in drops of microscopic size (~100 μm). The developed method of studying the processes of nucleation and growth of crystals in model alloys depending on their mass (size) can be applied in real conditions of mass crystallization. Keywords: model environment, droplet method, crystal nucleation, crystallization kinetics.

Heteronormative geographies and other sexual practices in rural Haryana, India

Kinship patterns and caste structures have a significant effect on Indian people’s lives. Rural Haryana has a strong caste-based kinship system organised around a heteronormative narrative that shapes associated societal and cultural values. This narrative centres on heterosexual marriage, which is arranged within the rules of kinship patterns. Such marital arrangements are viewed as the only space in which people can realise their sexual desires. This article aims to understand the diverse practices of people in rural Haryana that subvert this narrative to realise their sexual desires. The study adopted an ethnographic approach, using casual conversations as a data source to understand how sexuality is practised in rural areas under a strong kinship structure. In the paper, we argue that while the practices documented may seem subversive and countervailing, they contribute to concretising and maintaining the dominant social structure.

Multi-gradient structures by cold extrusion of strongly textured continuously cast commercially pure aluminum

During extrusion, the material is subjected to a heterogeneous deformation that results in the formation of gradients of microstructure and thus mechanical properties. In this study, using continuously cast commercially pure aluminum as a reference material, we show how a cast structure with coarse columnar grains affects the formation of these gradients during extrusion at room temperature. Characterization of the initial material as well as the extruded round bars by optical and electron microscopy, X-ray diffraction as well as by means of mechanical testing documents the formation of four characteristic annular sections. For extrusion along the casting direction there is a <100>/<111> double-fiber textured center with lowest hardness, followed by a <111> single-fiber textured ring with a hardness plateau, a double-fiber textured region with grains arranged alternatingly in an iris-like shape, and an (ultra-)fine grained surface layer with highest hardness. For extrusion opposite to the casting direction we find similar characteristics of the center section. With increasing distance from the center follow another double-fiber textured section with increasing hardness, a <111> single-fiber textured ring with nearly homogeneous hardness and a surface layer with a slightly rotated <111> fiber and highest hardness. The key finding is that the macroscopic anisotropy of the cast material, resulting from the grain size, crystal orientation and growth direction of the columnar grains, determines the local material flow during extrusion and thus leads to the formation of these different complex multi-gradient macrostructures that may provide unique properties for complex applications such as light-weight safety-relevant components.

Pulp ‐ Studio‐Based Research in Thin‐Shell Cast Paper Structures

This paper reflects upon a sequence of seven research studios, taught within a six-year timespan in three different architecture schools, in which we developed approaches to casting thin-shell (monocoque) paper structures at full scale. Processes of material selection and material harvesting/processing, formwork design and fabrication all informed the formal expression of the shells. In the context of architectural education, fabricating at full-scale can make structural principles accessible, but large constructions can be expensive for students, and can also create unnecessary material waste. This sequence of studios, called PULP, allowed students to fabricate spatial structures at full-scale using materials available at little to no cost. The large structures have the potential to biodegrade completely, creating no landfill waste, and no adverse impact in their final resting place. The dearth of research or precedents in cast‐paper‐as‐structure offers a unique opportunity for novel, basic or “blue skies” research in this area. Processual knowledge gained through leading this studio‐based research over several years has allowed us to focus more recent research on scaling-up and using material combinations and fabrication techniques that are simple and effective. The increasingly focused investigations and larger scale of the paper cast structures in the most recent (last two years of) studio research suggests that there is something like a paper-specific formal vocabulary in thin shell structures.

Experimental Simulation of Directional Crystallization of SiMo Cast Iron Alloyed with Al and Cr.

SiMo ductile cast iron combines ease of part fabrication with good mechanical properties, including a usable plasticity range. Its poor corrosion resistance inherited from grey cast iron could be alleviated through alloying with Al or Cr additions capable of forming a dense oxide scale protecting the substrate. However, the presence of Al and Cr in cast iron tends to make the material brittle, and their optimum alloying additions need to be studied further. The present work was aimed at investigating the effect of crystallization rates on microstructure changes during directional crystallization of SiMo-type alloys with up to 3.5% Al and 2.4% Cr. The experiment was performed using the Bridgman-Stockbarger method. The tubular crucible was transferred from the hot section to cold section at rates ranging from 5 mm/h to 30 mm/h with a 4/5 crucible length and then quenched. The introduced Al promoted graphitization up to a point, wherein, at the highest applied addition, the graphite precipitation preceded crystallization of the rest of the melt. A rising level of Cr in these alloys from 1% to 2.4% resulted in the formation of low and high contents of pearlite, respectively. The higher crystallization rates proved effective in increasing the ferrite content at the expense of pearlite. In the investigated cast iron samples with smaller applied alloying additions, Widmanstätten ferrite or ausferrite, i.e., fine acircular phase, were often found. The switch from directional crystallization to quenching caused a transition from a liquid to solid state, which started with nucleation of islands of fine austenite dendrites with chunky graphite eutectic separating them. As these islands expanded, they pushed alloying additions to their sides, promoting carbide or pearlite formation in these places and forming a super-cell-like structure. The performed experiments helped gather information concerning the sensitivity of the microstructure of SiMo cast iron modified with Al and Cr to crystallization rates prevailing in heavy cast structures.

Effect of purity on solidification structure and micro-segregation in a nickel-based single crystal superalloy

The purity of nickel-based single crystal alloys plays an important role in the final service performance of turbine blades as it impacts the solidification structure, elemental segregation, and inclusions of castings. The highest purity of superalloys studied before was of altogether around 10 ppm of contents of N and O produced by the triple purification process (VIM+ESR+VAR). However, the impact mechanism still remains controversial, and meanwhile whether a lower content of N and O still keeps the impacts on castings is not yet clear due to the lack of raw materials. A superhigh purity of second generation of nickel-based single crystal superalloy DD98M with the sum of N and O contents as low as 4 ppm (hitherto the highest purity of the superalloy as published), home-produced by electron beam smelting (EBS), was put on focus in this work. The effect of three levels of purity (N-doped, commercial, and EBS, corresponding to 21, 10, and 4 ppm for the sum of N and O contents, respectively) on the microstructure evolution (including primary dendrite arm spacing (PDAS), eutectic, micropores, and γ′ phase) and the solute segregation behavior at dendritic scale and nano scale (γ/γ′ interfaces) were systematically studied and the influencing mechanisms were elucidated. The results show that the PDAS decreased from 406 μm to 322 μm with the reduction of O and N from 21 ppm to 4 ppm, which was irrelevant to precipitation of the nitride or oxide inclusions. Instead, it was due to the decrease of diffusion coefficient D or the increase of equilibrium coefficient k, or the decrease of the critical nucleation supercooling and the incubation time of dendrites. The micro-segregation, the number and volume fraction of eutectic, and the number and voltage percentage of shrinkage pores and gas pores were all greatly decreased with the increase of purity. These changes were closely related to the reduction of PDAS and the reduction of fluidity of the remained liquid in the interdendrites during solidification. The morphology and the size of the γ′ phase were independent from the purity, while the segregation of alloying elements at the γ/γ′ interface changed remarkably with the variation of the purity.

Music as an Anti-Caste Counterpublic: Notes From North India

This article aims to understand the acts of resistance in the everyday music of oppressed caste communities and the repertoire of anti-caste musical performances in specific moments in history. The everyday soundscape has the potential to bring together shared experiences of displacement, casteism, and social exclusion. For dalit–bahujan singers, an engagement with music is a resource with which to ‘talk back’ to the structures of caste and to recast their identity. The practices of such musical form have also been part of the cultural transmission of an anti-caste narrative. Using printed material and oral narratives collected during fieldwork in selected regions of North India, this article explores anti-caste musical practices. It engages with the concept of ‘counterpublics’ and the implications of the term ‘anti-caste counterpublics’ for an understanding of anti-caste movements.

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%.