International Journal of Metalcasting最新文献

This study investigates the influence of magnetic fields on the microstructure and mechanical properties for the investment casting A356 Al–Si alloy. A356, known for its significant application in aerospace, defense, and automotive industries, was subjected to various intensities of magnetic fields generated by Helmholtz coils during the investment casting process. Additionally, the alloy was modified with the addition of Al–5Ti–B master alloy, and samples were subjected to T6 heat treatment. The aim was to explore the combined effects of magnetic field, grain refiner, and heat treatment on the alloy’s microstructural evolution and mechanical properties. The characterizations of A356 alloy included tensile strength, Vickers hardness, metallography, scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. The results indicated that magnetic fields applied during the casting process significantly influence the grain refinement of α-Al and the spheroidization of the eutectic silicon, leading to improve its mechanical properties. The study also examined the effects of magnetic fields on the distribution and morphology of eutectic silicon and Mg₂Si phases after T6 heat treatment. The findings of this research provide valuable insights in optimizing investment casting processes and enhancing the material properties of A356 alloy, which will offer potential applications in improving the quality and performance of cast components in various industrial sectors.

Due to severe acoustic attenuation, the effectiveness of single-source ultrasonic vibration (SUV) in dispersing reinforcement particles within Al matrix composites is limited, particularly when dealing with high weight fractions. In this study, a short-spacing multi-source ultrasonic vibration (MUV) technique, specifically quad-source ultrasonic vibration (QUV), was introduced to prepare SiC_p/A356 composites with a high weight fraction of 15wt.% SiC particles. The characteristic of acoustic streaming and the dispersion of particles were systematically investigated through numerical simulations and physical experiments. The results reveal that QUV mitigates acoustic attenuation and expands the potential cavitation region (exceeding the cavitation threshold of 1.1 MPa) compared to single-source ultrasonic vibration (SUV). The synergistic effect of multiple ultrasonic waves not only elevates cavitation intensity but also enriches the structures of acoustic streaming, significantly reducing agglomeration and improving the dispersion of SiC particles within the Al matrix. Without ultrasonic treatment, only a small proportion of SiC particles are embedded in the Al matrix, with an S_SiC/S_t ratio of merely 2.23%. However, as the number of ultrasonic sources increases, the agglomeration of SiC particles was relieved, and the resultant holes diminish. Remarkably, under QUV treatment, the holes in the composites virtually disappear, and the S_SiC/S_t ratio increases to 9.82%. Additionally, the composites exhibit superior mechanical properties, with a tensile strength of 200 MPa and an elongation of 7.0%, which are 10.5% and 38.5% higher than those achieved using SUV, respectively.

Zinc-modified hypoeutectic Al–Si–Cu–Mg–Cr–B alloy underwent a two-stage solution treatment at 520 °C for two hours and 550 °C for half an hour, followed by a two-stage aging treatment at 100 °C for three hours and 180 °C for eight hours. The impact of heat treatment and Zn addition on the eutectic Si phase, alloy compounds, and mechanical properties of the hypoeutectic Al–Si–Cu–Mg–Cr–B alloy was systematically investigated using an optical microscope, X-ray diffractometer, scanning electron microscope, energy spectrum analysis, and mechanical properties test. The findings revealed that heat treatment and Zn addition improved the size, morphology, quantity, and types of eutectic silicon phases and alloy compounds, as well as their mechanical properties. After heat treatment, the alloy displayed optimal characteristics with the addition of 0.3 wt% Zn. The eutectic Si phase of the alloy exhibited the most favorable morphology, the greatest variety of alloy compounds, the most favorable morphology and size, and the largest Q index, which is utilized to evaluate the overall tensile properties of the alloy. This indicates superior mechanical properties.

The current study is aimed to enhance the tensile performance of Al–Si–Cu–Mg cast alloys at both ambient and elevated temperatures. The investigation is focused on incorporating zirconium (Zr) as a primary alloying element, alongside nickel (Ni) and manganese (Mn), to assess their suitability for automotive engine applications. In Mn-containing alloys, tensile strength improvement was observed due to the precipitation of compacted α-Al₁₅(Fe, Mn)₃Si₂ and Al₆Mn phases. Meanwhile, Ni-bearing phases such as Al₃CuNi and Al₃Ni in Ni-containing alloys were found to inhibit crack propagation, thereby enhancing tensile properties. Results indicated that the addition of 0.75 wt.% Mn yielded comparable strength values to alloys containing 2–4 wt.% Ni at ambient temperature. Additionally, the presence of 0.25% Zr facilitated the precipitation of fine metastable L1₂-Al₃Zr particles, contributing to improved alloy strength. However, the introduction of 4% Ni resulted in the formation of Al–Cu–Ni particles rather than Al₂Cu, leading to a decrease in alloy strength upon aging.

Gas generation from molding materials creates a complex atmosphere in the mold–metal interface and is one of the primary causes of defects in cast components. Moisture, crystalline water, and decomposing binders are significant gas sources. The presence of volatiles and decomposing binder in the mold also affects the rate of heat absorption from the solidifying metal during the casting process. This work presents a measurement methodology to evaluate the rate and volume of gases generated from sand mixtures in combination with the temperature distribution and applied thermal analysis. The presented results show high reproducibility of the method. The thermal analysis results provide the start and end temperature of the binder decomposition reactions and the corresponding heat absorbed in this interval. The results obtained from the presented methodology can be used to validate the models/simulation tools developed to predict the gas evolution and related transport phenomena in the sand casting process.

This study explores the effect of bismuth on ductile iron to enhance its mechanical properties and to prevent the formation of chunky graphite. Various heats of ductile iron were produced with varying bismuth (0.000–0.010 wt%Bi). Microscopic examinations, Brinell hardness tests, and tension tests were conducted to characterize the samples. The results indicate that Bi influences the microstructure, nodule count, hardness, and tensile strength of the ductile iron, with optimal amount of Bi (0.005–0.007 wt%Bi) depending on section thickness. Bi prevented the carbide formation and increased the nodule count, leading to improved mechanical properties. In addition, the study demonstrated that Ce/Bi values of 1.29–1.60 were corresponding levels that showed optimal microstructure and properties. Thermal analysis demonstrated the inoculation effect of Bi addition by shifting TE_low and TE_high toward the stable eutectic temperature. Electron Probe Microanalysis (EPMA) results showed that Bi oxide and sulfide were found at the graphite cores as heterogeneous nucleation sites during solidification.

The primary objective of this investigation is to strengthen the mechanical and tribological properties of the cast Elektron 21 alloy (UNS M12310) by reinforcing its surface with a high entropy alloy (HEA) consisting of 0.3 wt% aluminum, 0.3 wt% copper, 0.1 wt% nickel, 0.1 wt% silicon, and 0.2 wt% tungsten fabricated by friction stir processing (FSP). The resulting Elektron 21/HEA surface composites (SCs) processed through casting followed by FSP were compared to the cast followed by FSPed Elektron 21 alloy, exhibiting significant enhancements in mechanical properties and wear resistance. The surface of the Elektron 21 matrix, which underwent casting followed by FSP, showed a homogeneous dispersion of HEA particles. These particles served as precipitates, creating geometrically necessary dislocations that hindered movement under applied force. The bonding between the HEA and the Elektron 21 alloy at the interface was excellent, and differential thermal contraction resulted in a strain misfit. Consequently, the microhardness, yield stress, and ultimate tensile stress of the FSPed Elektron 21/HEA SCs improved by 38%, 37%, and 32%, respectively, compared to the FSPed Elektron 21 alloy, although ductility decreased by 33%. Furthermore, the FSPed Elektron 21/HEA SCs showed a 33% enhancement in wear resistance and a 27% reduction in frictional force generation compared to the FSPed Elektron 21 alloy. The worn surfaces of the FSPed specimens showed that the FSPed Elektron 21 alloy revealed deep grooves, pits, micro-cutting, micro-grooving, and ploughing, while these features were absent in the FSPed Elektron 21/HEA SCs. These outcomes make it better suited for use in the aviation and automotive sectors.

Graphical Abstract

Binder Jetting technology is well established for the production of sand molds and cores for foundry use, owing to its flexibility and expansive design capabilities. A wide array of sand, aggregate, and binder combinations is commercially available. Utilizing these types of refractory materials in the casting process presents both technical and economic benefits and drawbacks. For intricate cast components, foundry technologists must assess the thermophysical properties of the mold material systems. With this knowledge, specialized high-performance material combinations may be employed in specific areas of the mold, while more economically viable systems are used for shaping the external mold support. This study primarily focuses on determining the heat capacity and thermal diffusivity and consequently the thermal conductivity using a specially developed analytical method. It investigates three different fundamental aggregates: silica, cerabeads^®, and chromite. The result’s range provides an overview of relevant characteristics for the selected material systems. Given that the properties of sand affect heat flow during casting and solidification, these newly determined values can be utilized in future simulations. Consequently, these findings aid in maintaining and enhancing the quality of critically stressed cast parts.