International Journal of Metalcasting最新文献

This study aims to assess the influence of the Mn to S ratios on the machinability and tensile behavior of GG20-gray cast iron brake drums. The effect of various Mn and S contents on microstructural characteristics such as type, size, and aspect ratio of graphite particles, interlamellar spacing of pearlite, and the distribution factor, size, and volume fraction of MnS were investigated. The microstructural results showed that a decrease in the Mn/S ratio to 5.1 and a decrease in the Ti/S ratio to under 0.11 promote the lengthy A-type graphite formation. Meanwhile, with the %Mn × %S value of about 0.08, the best uniform distribution of MnS inclusions has been obtained (about 55% of MnS inclusions are near A-type graphite flakes in the P1 specimen with %Mn × %S about 0.08 and Mn/S value of 5.1). Good machining in terms of less wear of the cutting tool and easier fragmentation of the chip in the sample with Mn/S value of 1.5 (0.65% Mn and 0.128% Sulfur) due to having more MnS inclusions, as well as a larger grain size graphite and its high aspect ratio have been obtained. The minimum tensile strength has been calculated to be 193MPa in the specimen with Mn/S value of 3.5 (0.55% manganese and 0.156% sulfur) due to the effects of higher sulfur content on changing the morphology of graphite to a higher aspect ratio. Meanwhile, at the same content of Mn (almost 0.55 wt%), further reduction of sulfur results in promoting E and D types of graphite in the microstructure.

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In this study, the in-situ ZrB₂/Al-Si5Cu3 aluminum alloy composites were fabricated through the salt-melt reaction route with different weight fractions of ZrB₂ reinforcements, i.e., 2.5%, 5%, and 7.5%. The composites were tested for their density, hardness, tensile strength, flexural strength, impact strength, and wear properties. The influence of reinforcement on the properties was studied concerning the wt.% of reinforcement. The increase in density of composites compared to the matrix material confirms the formation of the in-situ reinforcement phase. The microstructure showed a desirable distribution of reinforced particles over the matrix at all weight fractions of the reinforcements in the composites. The ZrB₂ particles formed in the matrix have particle sizes in the range from 255 nm to 955 nm and the grain size has been reduced from 242 microns to 110 microns as the result of particle-induced solidification. The hardness of the composites containing ZrB₂ reinforcements of 2.5, 5, and 7.5 wt.% showed improvement by 8%, 17.5%, and 34% respectively compared to the parent alloy. There is an improvement in the tensile strength and elongation for the wt.% of ZrB₂ up to 5 wt.%, from 115 MPa to 183 MPa, after which, there was a drop in the tensile strength. The detailed analysis of tensile fractography shows that the agglomerated ZrB₂ reinforced particles at higher weight fractions lead to a decrease in strength. The results of flexural strength also affirm the strength of 5 wt.% ZrB₂/Al-Si5Cu3 increased from the matrix material’s flexural strength of 337 MPa to 672 MPa. The wear study shows that the composite with 7.5 wt.% ZrB₂ possesses a higher wear resistance. However, the impact strength did not show any differences in the weight % of reinforcement.

Vortex-free high-speed stir casting (VFHSC) methodology can achieve uniform dispersion of particles in melt without air entrapment for fabricating particle reinforced composites, and it has been proved to be feasible for preparing micron-composites by this methodology. In this work, in order to study deeply on particles in nano-size magnitude in composites by this methodology, the preparation of 1.5 vol.% Nano-Al₂O_3p/Al–Cu–Mg–Si composite is also investigated. The proper stirring parameters for ideal particle dispersion are determined to prepare the materials. Porosity of the composite can be limited to 0.147 % under the VFHSC methodology. The composition and microstructure of ingots, including the incorporation of Al₂O₃ particles as well as the morphology of precipitated phases, are examined by OM, XRD, SEM, TEM, HRTEM and EDS. The nano-particles are incorporated ideally in the matrix with restricted aggregation and sedimentation, and the well-bounded Al₂O₃–Al interface possesses semi-coherent interface. Moreover, the VFHSC 1.5 vol.% Nano-Al₂O_3p/Al–Cu–Mg–Si composite exhibits obvious strengthening, limited ductility reduction, higher hardness as well as better wear resistance than those of matrix, validating the efficacy of the VFHSC methodology on fabricating 1.5 vol.% Nano-Al₂O_3p/Al–Cu–Mg–Si composite. The work proves that incorporating nano-particles in Al matrix by VFHSC methodology is feasible and efficient. The work presented in this paper proposes a viable approach for the fabrication of nanocomposites using the stir casting method, thereby offering valuable insights for further research on stir casting technology.

The hybrid aluminium alloy matrix composites are adopted in high-strength-to-weight ratio applications with technical benefits, including high strength, good hardness, better stability, and improved thermal stability. This research is enhancing microstructural and mechanical functional behaviours of the hybrid aluminium alloy (AA2024) nanocomposites by the blending actions of nano silicon carbides (SiC) particles and multi-walled carbon nanotube (MWCNT) via a two-step stir cast route. The contribution effect of SiC and MWCNT blending actions on metallography, physical/mechanical qualities, and resistance to corrosion individualities of hybrid AA2024 nanocomposites are studied by the procedure of the American Society for Testing and Materials (ASTM) and compared to monolithic cast AA2024 alloy characteristics. The hybrid AA2024 nanocomposite blended with SiC and MWCNT (weight percentages of 5 and 8%) exposed the specific tailored benefits like homogenous scattered reinforcements resulting in a lower percentage value of porosity (≤ 1%), excellent ultimate tensile strength of 330 MPa with acceptable elongation range of 10%, enhanced indentation resistance capabilities of 128 HV, specific toughness of 15.2 J/mm², and enhanced corrosion performance.

Mechanical reclamation is the de facto method of sand recycling in most foundries used to limit sand dumping and adhere to environmental regulations. The latter metal casting imperatives align with the United Nations Sustainable Development Goals of Responsible Production (Goal 12 - Ensure sustainable consumption and production patterns.). The crushing ratio, which essentially assesses the propensity of the sand to produce fine particles during moulding operations, is a critical property to predict the effectiveness of the mechanical reclamation process. This study assesses the crushing ratio of South African chromite sand. Five samples from the top worldwide producers were evaluated and compared. Rod milling was used to simulate mechanical reclamation. After testing, it was found that this crushing ratio varies between 1.68 and 1.93 after 9 minutes. Good statistical linear correlations were established between the crushing ratio of samples with Cr/Fe ratio, chromite content, and grain size. The investigation contributes to additional knowledge of chromite sand for foundry applications.

The 319-type alloy is one of the more widely used casting alloys for propulsion applications in the automotive space (i.e., E-motor housings for battery electric vehicles (BEV) and engine blocks for internal combustion engines (ICE)). For these 319-type applications that require the highest material properties and dimensional stability, a T7 (solution and quench followed by an artificial over-age) is used. The authors will demonstrate an innovative approach to investigate if the solution treatment stage can be scaled back significantly with adjustments in artificial age parameters, while achieving the same material properties and dimensional stability had a full solution treatment been used. The impact of achieving the objective of reducing the solution treatment stage would be the lower energy cost, eliminating or reducing the bottleneck (and/or increase capacity without capital investment) of the solution furnace, and finally reduce the CO₂ footprint of the overall heat treat process, all of which are critical for the future of the North American automotive casting manufacturing.

In the present study, a predictive analysis was performed to investigate the effect of droplet size, section size and type of the primary and secondary AlSi10MnMg alloys manufactured by vacuum-assisted high pressure die casting on wettability of the cast samples with water, since wettability influences corrosion resistance. Additionally, corrosion resistance of samples was studied using a linear polarization experiment. Contact angle (CA) measurements were performed on the specimens using a goniometer. An Artificial Neural Network was then developed to predict the contact angle values as a function of the predictor variables. The developed model was able to predict unseen CA values with excellent accuracy with the Pearson correlation coefficient of 0.96 between the predicted and observed CA. The modeling results show that the type of alloy (primary or secondary) is the most significant factor affecting CA, where almost 80% of CA variation is the result of changing the type of alloy. Confocal microscopy images demonstrate that this is attributed to the change in the heterogeneity of the surface, which affects contact angle values. The corrosion studies reveal that corrosion resistance is dependent on the type of alloy and surface roughness. The primary alloy possesses more corrosion resistance than the secondary alloy. This is due to the larger fraction of intermetallic compounds in the microstructure of the secondary alloy, which serve as galvanic sites in the corrosion reaction accelerating corrosion rate. Moreover, the non-uniformity induced by larger surface roughness is detrimental to the corrosion resistance of the samples. These results indicate that the data-driven approach used in this research is very promising not only to predict the performance, but also to optimize and design high-performance corrosion resistant surfaces of cast aluminum alloys.

The high-strength and thin-walled shells are extremely beneficial for not only rapid solidification of metal castings but also excellent for shell removal, its low residual strength and low solid waste discharge. In this work, short carbon fibers as reinforcement were induced into the shells. The strength of specimens and their fracture behavior at ambient temperature or high temperature in loading were investigated using scanning electron microscopy (SEM) and thermogravimetric-differential scanning calorimetry technique (TG-DSC). The results show that the bending strength of the shell progressively rises initially and then decreases rapidly with increasing content of fiber with a constant length. In particular, the shell reinforced with 0.42 wt% carbon fibers of length of 2.0 mm reaches a peak of green strength of 4.68 MPa and a peak of hot strength 16.06 MPa, respectively, approximately 89.47 and 61.20% higher than that of the unreinforced. Moreover, the peak of the fired strength of shell specimens containing 0.51 wt% fibers of length of 3.0 mm reaches 7.48 MPa, increasing by 61.20% in comparison with the unreinforced. However, the high-temperature self-weight deformation of the shell does not reveal positive correlation or monotonically increasing with the amount of fiber. Furthermore, the results revealed that the fracture types and failure patterns of fibers in shells were mostly related to fiber-fracture, pull-out and/or debonding during loading. These research results are beneficial to further improve this technology and promote the practical application to greatly reduce the generation and discharge of waste shells in the production of investment castings in the future.

In order to research whether the properties of a thin-walled plaster mold meets the production requirements in investment casting, this paper investigates a novel preparation technology for an adhesion-layer composite plaster mold. Based on a solid plaster mold, a single adhesion layer was applied to the outer surface for preparing the composite mold. An adhesion layer was deposited using silica sol as an adhesive, while refractory materials served as sand particles. Effects of specimen wall thickness on the strength, permeability, and thermal conductivity of composite mold were investigated. The results reveal positive correlation between wall thickness of the composite mold and its strength properties. Permeability and thermal conductivity, on the other hand, decrease with increasing wall thickness. Notably, at wall thickness of 3.5/4 compared to original specimen, significant improvements are observed. Specifically, compared to original solid mold, green specimens exhibit an increase of 4.64% and 7.80% in flexural and tensile strength, respectively. For fired specimens, the increases are even more remarkable, reaching 28.87% for flexural strength and 28.71% for tensile strength. Moreover, the increment of permeability and thermal conductivity with fired specimens was 169.33% and 9.45%, respectively. The monoclinic ZrO₂ (m-ZrO₂) characteristic peak appeared in the Raman spectra of the composite mold. It is shown that Zr4+ plays an important role in the accumulation of anion groups with the gypsum system, and then improves the macroscopic strength of mold. The obvious physical interface is observed between the plaster matrix and adhesive layer. It is noteworthy that the gypsum matrix and adhesion layer demonstrate varying abilities to resist structural damage, with a macroscopic fracture of gypsum matrix being more likely to occur prior to adhesion layer. Composite plaster mold exhibits a symmetrical and stable crystal structure and has better fracture deformation resistance compared to a solid mold. Fracture of the mold can be attributed to three types of failure: fiber failure, delamination failure, and damage between fibers and the matrix. These failure types are major factors influencing macro fracture of composite molds.

To improve coke performance in the cupola, the authors discovered that coke used in blast furnaces [low coke reactivity index (CRI), high coke strength after reaction (CSR)] exhibits higher strength than foundry coke and may provide better performance due to larger coke pieces reaching the melt zone. Coke strength and sizing are extremely important in a cupola because the coke must reach the melt zone intact, stay in the melt zone long enough to replenish the coke bed, provide heat for melting and carbon pickup to the liquid iron. This research evaluates the cupola performance difference between cokes of high and low CRI. In addition, efforts were made to identify differences in characteristics of these cokes.