Cast Alloy Research Articles

Microstructure and mechanical properties of Mg-Gd-Zn-Zr alloy after hot extrusion

The microstructural evolution and mechanical properties of the Mg-6Gd-1Zn-0.5Zr (wt.%) alloy during heat treatment and composite extrusion were studied in this work. The (Mg, Zn)3Gd phase and a small amount of 14H long-period stacking ordered (LPSO) phase formed in the cast alloy, and more lamellar 14H-LPSO phases formed in the alloy during homogenization treatment. The bimodal grain structure composed of coarse deformed microstructure and fine dynamic recrystallization (DRX) grains formed in the alloy after extrusion. The γ′ phase and β´ phase precipitated after the extrusion process and after the solution and aging treatment, respectively. The kinking of the lamellar 14H-LPSO phase occurred during the extrusion process. DRX grains formed in the alloy during extrusion process through continuous dynamic recrystallization (CDRX), particle stimulated nucleation (PSN), and kinking-assisted DRX. The yield strength, tensile strength and elongation of the extruded alloy were 227MPa, 320MPa, and 20.68%, respectively. The strength and elongation of the extruded alloy are enhanced by the strengthening effect from the bimodal structure, kinking of the LPSO phase, and LPSO phase. The tensile properties of the alloy decreased after the solution and aging treatment. The bimodal structure and kinking of the LPSO phase disappeared after the solution and aging treatment.

Purification of U from U-10Mo scrap generated during the fabrication of high performance research reactor fuel

ABSTRACT A low enriched U-Mo alloy fuel is under development to replace highly enriched U fuels currently used in United States high performance research reactors. The alloy casting and fuel fabrication processes will generate scrap streams containing low enriched U (LEU) which must be recovered. Solvent extraction processes were designed using the Argonne Model for Universal Solvent Extraction (AMUSE) to purify solutions containing 20 and 50 g/L U. The feed for the solvent extraction processes was prepared from solutions generated from the dissolution of U-10Mo-Zr foils and U-10Mo-Zr-Al mini-plates. The U purification processes were demonstrated using two, 16-stage banks of miniature mixer-settlers. The solvent extraction experiments demonstrated that all design objectives for the U purification processes could be met. The U recovery in the product stream for each flowsheet was ≥99.9%. The flowsheet demonstrations also showed that the purity of the U Product will meet the requirements of the ASTM International C1462-21 specification for LEU metal enriched to less than 20% 235U. The AMUSE modeling for both flowsheet demonstrations was validated by comparing predicted and measured concentrations of U, Mo, and Zr in the exit streams and stage samples at steady-state conditions in the mixer-settlers.

Effect of grain boundary phase formed by Mn addition on initiation and propagation of fatigue cracks in homogenized Cu-6Ni-1.3Si alloy

High-strength cast Cu alloys often contain substantial quantities of alloying elements that promote the nucleation of heterogeneous particles, particularly at grain boundaries (GBs). In the Cu-6Ni-1.3Si alloy, intermetallic compounds such as Ni2Si form within the matrix and along the GBs following homogenization. Ni2Si particles within the matrix are homogeneously nucleated with diameters of a few tens of nanometers, which enhances matrix strength. However, heterogeneously nucleated Ni2Si particles at GBs, which can be several micrometers in size, negatively impact overall strength. To improve the strength of Cu-6Ni-1.3Si alloy, 2.1 wt% Mn was added. This Mn addition led to the formation of plate- or film-shaped intermetallic compounds, specifically Ni16Si7Mn6 (G-phase), at GBs after homogenization. Despite the Mn addition, Ni2Si precipitates with diameters of a few tens of nanometers still formed within the grains, but these were more densely distributed in the Mn-added alloy compared to the Mn-free alloy. Fatigue tests conducted on round bar specimens of both alloys showed that Mn addition enhanced fatigue strength. This enhancement is attributed to the suppression of both crack initiation and propagation along the GBs and within the matrix.

Integration of confocal chromatic spectroscopy into a test bench concept for safety inspection practices, with focus on stress detection

Evaluating casting’s mechanical stress is of significant interest from a safety inspection’s point of view. Residual stress, in particular, leads to an early or even immediate failure of some parts. Therefore, several methods exist to determine casting’s external and internal strain leading to stress. By determining the state of stress and residual stress, it is possible to design casting parts that are much safer. The present concept of a test bench shows a new way of inspecting parts for safety reasons using an optical fiber confocal chromatic sensor to measure strain. The method is based on the deep-drilling method, where a minimal invasive hole is placed at an area of interest in the first step. In a second step, this hole is then precisely measured to be able to map the borehole. From this information, conclusions can be drawn of any forces acting on the inspected part. In this case, the concept of the test bench uses gun drills to place boreholes measuring 6.0 mm in diameter with up to 500.0 mm in depth, and for the inspection, a confocal sensor with a precision of ± 100.0 nm in dissolving distances is used. This work focuses on evaluating the test bench’s precision in conducting such measurements and on how an external thermal load and mechanical load influence the results when conducting differential measurements. The experiments are performed on typical cast alloys such as iron cast and Zamac.

Correction: Effect of Horizontal Continuous Casting Parameters on Cyclic Macrosegregation, Microstructure, and Properties of High-Strength Cu–Mg Alloy Cast Rod

Correction: Effect of Horizontal Continuous Casting Parameters on Cyclic Macrosegregation, Microstructure, and Properties of High-Strength Cu–Mg Alloy Cast Rod

Studies of SiC‐Filled Al6061 Metal Matrix Composite Optical, Mechanical, Tribological, and Corrosion Behavior with Strengthening Mechanisms

The objective of the current study is to produce metal matrix composites (MMCs) using ultrasonic‐assisted stir casting and Al6061 alloy reinforced with silicon carbide (SiC) microparticle reinforcement in weight percentages of 0, 2, 4, and 6. The microstructural alterations of Al6061–SiC composites are investigated using a scanning electron microscope (SEM) equipped with an energy‐dispersive X‐ray (EDAX). By adding more nucleation sites for the formation of smaller grains, SiC reinforcement of the Al6061 matrix encourages grain refining. The SiC addition significantly changes the microstructure of Al6061 composites, enhancing their mechanical qualities. In addition to increasing density by 0.6%, hardness by 33%, and tensile strength by 33%. The increased SiC content dramatically decreases elongation by 42%. The strength of Al6061–SiC MMCs is predicted using several strengthening mechanism concepts as part of the continuing investigation. For Al6061–SiC composites, the strengthening contribution from thermal mismatch is more significant than that from Orowan strengthening, Hall–Petch mechanism, and load transmitting effect. Grain refinement interactions, load transmission mechanisms, and the strengthening effects of CTE differences and dislocations between matrix and reinforcement particles are studied. The composite with 6‐weight percent SiC reinforcement performs better in dry sliding wear and corrosion resistance.

Tool wear and surface characteristics of TiAlN/AlCrN insert in high-speed turning of bimetal aluminium alloy-grey cast iron engine block

This study investigates the tool wear and surface characteristics of TiAlN/AlCrN-coated inserts during high-speed turning of aluminium alloy and grey cast iron (GCI) in engine blocks. Cutting performance was evaluated at a constant speed of 1,130.4 m/min and a feed rate of 0.18 mm/rev over 300 shots (the number of intermittent cuts). SEM-EDX and roughness analysis revealed abrasion and adhesion as the main wear mechanisms, with a maximum flank wear of 1.14 mm, primarily due to GCI’s abrasive nature. Surface roughness measurements for aluminium HD2 and GCI were 7.09 µm and 9.15 µm, respectively. The results highlight the effectiveness of TiAlN/AlCrN coatings but show eventual breakdown under GCI, offering insights for improving tool design in bimetal machining.

Corrosion evaluation of Al-Cu-Mn-Zr cast alloys in 3.5% NaCl solution

Corrosion behavior of cast Al-Cu-Mn-Zr (ACMZ) and RR350 alloys was compared to a cast 319 alloy in 3.5 wt.% NaCl. After 168 h immersion, ACMZ and RR350 alloys suffered from preferential attack adjacent to intermetallic particles decorated at grain boundaries while the attack in 319 occurred in eutectic Al-Si dendritic boundaries. Electrochemical data allowed semiquantitative comparison of alloy resistance to corrosion initiation, and ACMZ type alloys, including RR350 and three alloys with higher Cu, were considered more resistant than 319 due to the absence of deleterious Si particles. In case of 319, such Si particles presumably drove higher micro-galvanic influence to initiate and sustain Al corrosion. With lower susceptibility to corrosion initiation, ACMZ alloys should exhibit higher or at minimum similar resistance compared to cast 319.

A strain integrated gas infusion process (SIGI) for magnesium alloy castings

This study presents a Strain Integrated Gas Infusion Process (SIGI) to manufacture high-performance cast AZ91 magnesium alloys without the addition of secondary alloying elements/reinforcements or secondary processing. The current SIGI process involves a combination of agitation and localized rapid heat extraction via strain integration and high-energy gas infiltration. The SIGI casting process has been compared systematically with conventional techniques. The critical process parameters, including hole diameter, bubble diameter, and flow rate, have been optimized through numerical calculations, simulations, extensive experiments, and comprehensive analysis. The study also focused on investigating the effect of gas bubbles on the molten metal and established the mechanisms involved in improved solidification. Gas infusion combined with strain integration impacts the solidification process, ensuring uniform alloying element distribution and reducing segregation and microporosity. This manufacturing strategy eliminates casting defects such as segregation and microporosity, resulting in a non-dendritic homogeneous microstructure. The significant refinement in morphologies of both primary (α-Mg dendrites) and secondary (β-Mg17Al12 phase) phases highlights the success of the current SIGI process. Compared to the conventional casting processes, a remarkable improvement in strength-ductility synergy is achieved in the current SIGI process. The scientific know-how and efficiency of the current SIGI process are established and discussed in detail, providing a promising solution to address the existing challenges encountered in magnesium alloy billet castings. The SIGI process improves the mechanical properties and corrosion resistance of billet-cast magnesium alloys. The SIGI process is suitable for the billet casting, offering significantly improved properties but faces limitations in complex mold casting applications. The billets casted by SIGI process can be used as a high-quality precursors for downstream processes to create industrial components.

Effect of Microporosity and Precipitation Phases on the Quality Index of AZ Series Magnesium Alloy Castings with Varying Grain Sizes

Effect of Microporosity and Precipitation Phases on the Quality Index of AZ Series Magnesium Alloy Castings with Varying Grain Sizes

Effect of in-situ submicron Al3Ti particles on grain refinement and strengthening of Al–Zn–Mg–Cu-based alloy

Extensive research has been conducted to improve the efficiency for grain refinement of aluminum cast alloys. Herein, we propose a novel strategy to significantly reduce the cast grain size using in-situ submicron Al3Ti particles. The ZnO nanoparticles with enhanced wettability via mechanical stirring process provide finely dispersed α-Al2O3 particles, which serve as heterogeneous nucleation sites for primary Al3Ti particles. A large number of primary Al3Ti nuclei are formed from the α-Al2O3 particles without coarsening even under a relatively slow cooling rate. As a consequence, the size of Al3Ti particles was reduced to approximately 600 nm, resulting in the fine cast grain size of approximately 20 μm. Furthermore, a sheet made of the refined cast alloy has reduced recrystallized grain size and simultaneously improved strength and ductility.

Impact of Combined Zr, Ti, and V Additions on the Microstructure, Mechanical Properties, and Thermomechanical Fatigue Behavior of Al-Cu Cast Alloys

The effects of minor additions of the transition elements Zr, Ti, and V on the microstructure, mechanical properties, and out-of-phase thermomechanical fatigue behavior of 224 Al-Cu alloys were investigated. The results revealed that the introduction of the transition elements led to a refined grain size and a finer and much denser distribution of θ″/θ′ precipitates compared to that of the base alloy, which enhanced the tensile strength but reduced the elongation at both room temperature and 300 °C. Constitutive analyses based on theoretical strength calculations indicated that precipitation strengthening was the primary mechanism contributing to the strength of both tested alloys at room temperature and 300 °C. The out-of-phase thermomechanical fatigue test results showed that the addition of transition elements caused a slight decrease in the fatigue lifetime, which was mainly attributed to the reduced ductility and higher peak tensile stress at low temperatures. During the fatigue process, the transition element-added alloy exhibited a lower coarsening ratio, indicating higher thermal stability, which mitigated the negative impact of the reduced ductility on the fatigue performance to some extent. Considering their various properties, the addition of Zr, Ti, and V is recommended to improve the overall performance of Al-Cu 224 cast alloys.

Improving heat transfer in an air-cooled engine by redesigning the fins

Heat transfer modelling and simulation were carried out in a single-cylinder, four-stroke, air-cooled engine to evaluate the heat transfer rate of the engine block. The modelling studies of cylinders with different numbers of fins and different geometry were performed using the SolidWorks computer platform. The tested components were made of 6063-T6 aluminium alloy castings. The simulation concerned different numbers of fins as well as changing the geometry of fins with circular and rectangular perforations. The results of the studies showed the possibility of improving the power to mass ratio for cylinder efficiency and heat transfer rate. It was shown that a large number of fins leads to an increased heat transfer rate, but it affects the overall engine efficiency due to the increase in the total engine mass. Circular perforation is a better design solution than rectangular perforated fins with the same cross-section. Circular perforation provides a lower engine cylinder mass and gives more than 4 % better heat transfer rate. The perforation size was tested using circular perforations with a diameter of 7.14 mm, 8.5 mm and 10 mm. With a 7.14 mm diameter perforation the heat transfer rate increases slightly compared to the other tested ones, while a 10 mm diameter perforation provides the best mass reduction.

Research on frozen sand mold casting technology for complex thin-walled aluminum alloy castings

With the growing emphasis on environmental sustainability and the modernization of the manufacturing sector, the pursuit of eco-friendly practices within the foundry industry has become a critical objective. This paper proposes an innovative solution for environmentally friendly casting: the digital frozen sand mold casting technology. To evaluate its effectiveness, this study analyzed complex thin-walled grid rudder aluminum alloy castings. A comparative analysis was conducted between the binder jetting 3D printing and frozen sand mold (sand mold milling) casting processes. By utilizing Anycasting software, the research explored the filling and solidification processes of ZL101 grid rudder castings under varying mold conditions, aiming to predict the distribution and severity of shrinkage defects. Validation of this approach indicated a machining error of ±0.25 mm for frozen sand molds. The dimensional accuracy of the grid rudder castings achieved a casting tolerance grade of 9 (CT9), and the direct recovery rate of used sand exceeded 98 %, thus positioning this method as a viable alternative to 3D-printed resin sand. Additionally, the study assessed the economic feasibility of frozen sand mold casting technology in terms of resource consumption and production efficiency. The research findings hold significant relevance, offering valuable insights and guidance for traditional casting enterprises seeking to adopt sustainable development practices through the application of leveraging frozen sand casting technology.

Comparative analysis on high temperature tribological behaviour of additive manufactured and cast AlSi10Mg alloy

Abstract In recent years, additive manufacturing (AM) of AlSi10Mg, a material widely used in the aerospace and automotive sectors, has gained considerable interest for its ability to produce intricate shapes with improved mechanical properties. This proposed study aims to experimentally assess the high-temperature tribological performance of as-printed AlSi10Mg and compare it with traditionally cast AlSi10Mg to determine its suitability for high-temperature tribological applications. Samples of AlSi10Mg were manufactured via powder bed fusion, followed by tribological testing at elevated temperatures (30 °C, 100 °C, 200 °C, and 300 °C). The performance of both printed and cast AlSi10Mg pins was compared against an EN31 disc. The microstructure, worn surface, and wear debris of both printed and cast AlSi10Mg were examined using XRD and SEM with EDX analyses. As the load and temperature increase, both printed and cast AlSi10Mg materials demonstrate an increase in wear rate and friction coefficient. The wear rate of printed AlSi10Mg decreased by 60% compared to cast AlSi10Mg at higher temperatures. There is a consistent trend in the coefficient of friction between printed and cast AlSi10Mg samples at low temperatures and loads. Abrasive wear predominantly occurs in both printed and cast AlSi10Mg samples at 30 °C within a load range of 10 to 20 N, while adhesive wear predominates in the same samples at temperatures ranging from 100 °C to 300 °C with an applied load of 30 N. At low temperatures, smaller wear debris is observed, whereas at high temperatures and under a load of 30 N, larger wear debris is observed for both cast and printed AlSi10Mg samples.

Coupling CALPHAD Method and Entropy-Driven Design for the Development of an Advanced Lightweight High-Temperature Al-Ti-Ta Alloy.

In this study, a new lightweight Al-Ti-Ta alloy was developed through a synergistic approach, combining CALPHAD methodology and entropy-driven design. Following compositional optimization, the Al87.5Ti6.25Ta6.25 (at.%) alloy was fabricated and isothermally heat-treated at 475 °C for 24 h to attain equilibrium. X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) analyses revealed a dual-phase microstructure comprising a 50 vol.% FCC matrix enriched in Al and 50 vol.% Al3(Ti,Ta)-type intermetallic phase (IP). Notably, the FCC phase exhibited a high-melting transition temperature of 660 °C, surpassing conventional Al-Si cast alloys. Phase-specific nanomechanical properties were evaluated using Nanoindentation. Microindentation tests demonstrated exceptional microhardness of approximately 3300 MPa. These results indicate the alloy's superior hardness compared to conventional alloys such as Al-Si (A390), 7075 Al alloy, and CP-Ti, even exceeding Ti-64 alloy at a 15% lower density. The alloy's stability under prolonged heat treatment at 475 °C, reflected by stable phases, microstructure, and mechanical properties, highlights its enhanced thermal stability, which can be attributed to entropy-driven phase stabilization. This study underscores the effectiveness of integrating entropy-driven design strategy with CALPHAD predictions for the accelerated development of advanced Al-based alloys.

Achieving refined microstructures and improved mechanical properties in a cup-shaped Mg-Gd-Y-Zr alloy casting by novel near-liquidus squeeze cast process

We have recently proposed a novel process named low frequency electro-magnetic stirring assisted near-liquidus squeeze cast (NSC), which has been shown effective grain refinement effect in pure Mg and binary Mg-RE alloys. In this work, the NSC process was introduced for fabricating of a cup-shaped casting by Mg-Gd-Y-Zr alloy (VW103K). The cup-shaped VW103K alloy castings fabricated by NSC process show good surface quality and dimensional accuracy, as well as with fine microstructures and no megascopic pores and surface shrinkages. At the cross section of the cup-shaped castings, the grain size, phase compositions and hardness are nearly equally distributed. The NSC processed VW103K alloy show finer average grain size and higher yield strength than that of gravity cast, squeeze cast and rheo-squeeze cast counter parts. Pouring temperature is critical and may influence the microstructure and mechanical properties of NSC processed alloys. With the decrease of pouring temperature from ∼660 to ∼630 °C, the grain size is decreased initially and then coarsened slightly, while the distribution of eutectic phase gets worse continuously. An optimal pouring temperature range of ∼660 to ∼640 °C was obtained for fabricating of VW103K alloy. The mechanisms on formation of fine microstructures in NSC processed VW103K alloys is the combined effects influenced by applied pressure, pouring temperature and the shape of mold cavity.

Grain refiner fabricated by spark plasma sintering for hypoeutectic Al–Si alloy cast and its refining ability

Grain refiner fabricated by spark plasma sintering (SPS) for an as-cast hypoeutectic Al–Si alloy were proposed. The proposed grain refiner contains Al3Ti and Na flux particles in an Al-11 mass%Si alloy matrix. Through SPS, the grain refiner were obtained without any reaction between the Al3Ti particles, Na flux particles, and Al-11 mass%Si alloy matrix. Casting tests were conducted using the proposed grain refiners, and the refiners reduced the dendrite cell size and the dendrite arm spacing of the primary α-Al phase, as well as the lamellar spacing of the eutectic structure. The eutectic Si phase changed to a granular shape upon the refinement of the eutectic structure. Furthermore, the tensile strength and ductility of the as-cast Al-11 mass%Si alloy were drastically improved by adding the proposed grain refiner. This improvement was attributed to the refinement and granulation of the eutectic Si phase.

Microstructure and Mechanical Properties of Laser Powder Bed Fusion 3D-Printed Cu-10Sn Alloy

This study investigated the optimal process conditions and mechanical properties of Cu-10Sn alloys produced by the powder bed fusion (PBF) method. The optimal PBF conditions were explored by producing samples with various laser scanning speeds and laser power. It was found that under optimized conditions, samples with a density close to the theoretical density could be fabricated using PBF without any serious defects. The microstructure and mechanical properties of samples produced under optimized conditions were investigated and compared with a commercial alloy produced by the conventional method. The hardness, maximum tensile strength, and elongation of the samples were significantly higher than those of the commercially available cast alloy with the same chemical composition. Based on these results, it is expected to be possible to use the PBF technique to manufacture Cu-10Sn products with complex 3D shapes that could not be made using the conventional manufacturing method.

Investment casting of porous Mg-alloy networks biomechanically tuned for bone implant applications

Manufacturing technology has been refined and described for the fabrication of honeycomb-based bioresorbable networks for temporal bone replacement applications. Two novel techniques, digital light processing and investment casting, were utilized to produce customized, shape-optimized cellular constructs with additional orifices promoting tissue ingrowth during osteo-regeneration. For this purpose, a conventional magnesium casting alloy (AZ91) was chosen. Numerical simulations were conducted to predict the compressive behavior of the proposed biodegradable lightweight scaffolds. Spatial castings were adjusted to possess mechanical properties comparable to the ones of cortical or trabecular bones. Two kinds of protective coatings (plasma electrolytic oxidation and organic ones based on natural polyphenols from tea extract) were deposited and characterized. They can be utilized to control the degradation rate during exploitation to achieve a predictable implant lifespan. The elaborated layers aim to mitigate the rapid corrosion of magnesium substrates by prolonging their bioresorption time and thus expanding their applicability in osseointegration. To evaluate this assumption, immersion tests in phosphate-buffered saline were performed, showing better chemical resistance of PEO coating and as-cast sample (for both mass gain by below 1%), and visible increase in mass of sample coated with organic coating (increase by almost 5%). Compressive strength results from numerical approach were further validated by experimental compression tests, showing that PEO coating deteriorated compressive strength by almost 3%, and organic coating improved it by over 9%. Results achieved in numerical approach were better than expected for stiffer sample, and slightly lower for the one with bigger pores.