Al-Si Cast Alloys Research Articles

Pengaruh Variasi Bahan Pengikat Terhadap Kekuatan Cetakan Pasir, Permeabilitas, Fluiditas, Kekerasan Logam dan Kualitas Hasil Pengecoran Logam Paduan Al-Si Dengan Metode Gravity Casting

<em>This research was conducted to investigate the effect of binder variation including bentonit, lapindo mud, and portland cement on the silica molding sand strength, permeability, fluidity, metal hardness and the quality of Al-Si alloy casting by using gravity casting method. The experimental design was used on this research and analyzed by using descriptive data analysis. The result showed molding sand containing 15% lapindo mud binder had the highest wet compressive strength (8,73 N/cm<sup>2</sup>). The molding sand containing 15% portland cement binder had the highest dry compressive strength (>32 N/cm<sup>2</sup>). The highest wet tensile strength was resulted by the molding sand containing 15% bentonit binder (3,33 N/cm<sup>2</sup>), while the highest dry tensile strength was resulted by the molding sand containing 15% portland cement binder (18,60 N/cm<sup>2</sup>). The highest wet shear strength was resulted by the molding sand containing 15% portland cement binder (0,57 N/cm<sup>2</sup>), while the highest dry shear strength was resulted by the molding sand containing 15% portland cement binder (1,03 N/cm<sup>2</sup>). The molding sand containing 15% bentonit binder had the finest permeability (210 mm/minute). In the real practical application, the molding sand containing 15% portland cement binder was unable to result an appropriate molding strength when manually compressed in cope and drag (casting flask), thus it was unable to use as metal pouring media. The molding sand containing 15% lapindo mud binder had the finest fluidity but it had the lowest hardness (120,30 HV). The molding sand containing 15% bentonit binder resulted the best Al-Si alloy casting quality and the highest hardness (129,60 HV).</em>

Effect of temperature on the mechanical properties of Al–Si–Cu–Mg–Ni–Ce alloy

High-temperature performance is a key factor to concern for the application of cast Al–Si alloys. The evolution of microstructures and mechanical properties of a multiphase Al–Si–Cu–Mg–Ni–Ce alloy during tension in a temperature range from 25 °C (ambient temperature) to 425 °C was investigated. The results show that the main strengthening precipitates of the alloy are θ′ and Q phases. They are stable at 25–250 °C, while dissolve rapidly above 250 °C during tension. The damage initiates and propagates in the form of cracking of brittle phases. The fracture mechanism transforms from quasi-cleavage to coexistence of quasi-cleavage and dimple as temperature increases. The Ce-bearing phase Al20Ti2Ce promotes the damage occurrence below 350 °C while hinders crack propagation at 425 °C. The ultimate tensile strength (UTS) and yield strength (YS) decrease as the tensile temperature increases. The decreasing rate of UTS can be divided into three stages which is associated with the decreasing rate of strengthening precipitates. An empirical constitutive equation is proposed to describe the relationship between UTS and tensile temperature. It provides a good estimation for both cast and wrought Al alloys and the predicted strengths are in good agreement with the experimental results.

Extending the Tolerance of Iron in Cast Al-Si Alloy

Extending the Tolerance of Iron in Cast Al-Si Alloy

High-cycle fatigue failure analysis of cast Al-Si alloy engine cylinder head

Due to the premature fracture of several cast Al-Si alloy cylinder heads at the same position during high-cycle fatigue (HCF) bench test, the HCF failure analysis including finite element simulation, microscopic observation and fatigue tests were conducted to determine the root cause of the failure. The results show that the external load was not the main cause of the fracture. The large defects with complex shapes and low compactness near the surface, and the poor surface finish of the water jacket surface are the main causes for the quick initiation of cracks. Furthermore, the alloy at the failure location exhibits relatively high porosity and secondary dendrite arm spacing, accelerating the crack propagation rate. Compared with the alloy at the non-failure locations, the yield strength, ultimate tensile strength and elongation of the alloy at the failure location are reduced by 9.3%, 25.8% and 65.3%, respectively. The fatigue life of the alloy at the non-failure location is several times the alloy at the failure location, verifying that the local large defects and poor microstructure characteristics are the main causes for the low HCF strength of the cylinder head.

Fatigue Behavior of an Al-12.7Si-0.7Mg Alloy Processed by Extrusion and Heat Treatment

The fatigue life of a hot extruded Al-12.7Si-0.7Mg alloy under T1, T4, and T6 conditions was studied. The microstructure and tensile properties of the alloy were investigated in order to analyze the fatigue behavior. The results of the fatigue test showed that an extruded Al-12.7Si-0.7Mg alloy provided greater fatigue life compared to a cast Al-Si alloy, which was explained by the refined microstructure characterized by fine Si particles uniformly distributed in the Al matrix of fine equiaxed grains promoted by hot extrusion. The fatigue property of the alloy in T6 treatment was higher than that in the T4 and T1 conditions due to strengthening precipitation.

A new microstructure‐based multiaxial fatigue life prediction model for A319 casting alloys

AbstractThis paper describes a microstructure‐based multiaxial nonproportional fatigue life prediction model applied to A319 alloy. The materials made with different casting cooling rates and Sr modification are characterized and quantified in terms of secondary dendrite arm spacing, size, and aspect ratio of eutectic Si particles. Multiaxial nonproportional fatigue tests have been performed on six groups of A319 alloys to systematically analyze the effect of microstructure and loading path on the fatigue properties of Al–Si cast alloy. The first part of the paper is focused on microstructure quantitative characterization to determine the influence of different casting conditions, followed by stress response behavior and fatigue fracture analysis. Finally, a new multiaxial fatigue life prediction model for Al–Si alloy is proposed, for which 56% of the data points fall in the bound lines of factor of 2 and 83% of the data points fall in the bound lines of factor of 3.

Effect of FSP on mechanical properties, wear and corrosion behavior of A356 Al alloy

Grain refining and microstructure homogenization are fundamental challenges for enhancing the performance of the materials. One of the effective ways to solve these challenges is the Friction stir processing (FSP) technique. This paper investigates the FSP parameters’ impact on the microstructure, hardness, wear, and corrosion behavior of A356 Al–Si cast alloy. The FSP parameters are rotational speed (355–900 rpm), trasverse speed (10–40 mm min−1), and two different tool geometries. The results revealed that the intense plastic deformation and dynamic recrystallization fragmented the needle-shaped eutectic silicon particles. The particle size change was more pronounced as the rotational speed was increased than the transverse speed and the pin profile tool geometry. The fragmented and homogeneously distributed Si particles in the investigated alloy increased their hardness, wear, and corrosion resistance compared with those of the unprocessed base metal. The hardness increased by two times, and the wear rate reduced by ten times, while the corrosion rate decreased by 200 times than the BM at lower tool rotational speeds and higher transverse speed. The Possible reasons were discussed for these enhancements.

Influence of Mold Material on the Mold Stability for Foundry Use

In CO2 molding process, sodium silicate is used as a binder to form a chemical bond to have high strength, good dimensional accuracy, etc. as compared to green sand mold. The mold materials are for present investigation wis. silica sand (ss), red mud (rdm), blast furnace slag (bfs), ferrochrome slag (fcs) and olivine sand (olv). This paper investigates the mold properties such as shear strength, compressive strength, hardness, and permeability as per to the American Foundrymen Society (AFS) standard. The mold properties of these mold materials were investigated for the stability as a mold, as compared with silica sand mold for foundry use. And also investigated the effect of mold material on the morphology of phases of the microstructure of Al-Si alloy cast in a different mold. The result shows that the mold properties of blast furnace slag were better as compared to silica sand mold; the mold properties such as shear strength, compressive strength, hardness and permeability of blast furnace slag mold and silica sand mold are 7.2 psi, 17.5 psi, 88, 630; 6.9 psi, 15.4 psi, 92, 480 respectively. The A319 alloy cast in slag mold having less porosity, lower value of secondary dendritic arm spacing (SDAS), and high tensile strength as compared to silica sand mold.

Microstructure, Hardness, Tensile Strength, and Sliding Wear of Hypoeutectic Al–Si Cast Alloys with Small Cr Additions and Fe‐Impurity Content

Herein, the influence of Cr additions on the solidification parameters, as‐cast microstructures, and mechanical properties of Al–Si alloys with Fe‐impurity is investigated. Al–Si–Cr alloys with 3% and 7% Si and 0.25% and 0.40% Cr are developed. Solidification experiments are performed using an instrumented cooling casting apparatus permitting the obtainment of vertical upward‐solidified ingots. The morphological and phase structures are characterized by optical and scanning electron microscopy and X‐ray diffractometry. Hardness, tensile, and dry sliding wear tests are conducted to determine the mechanical properties. The Cr addition to the Al–Si alloys leads to the formation of α‐Al(Si, Fe)Cr interdendritic precipitates, suppressing the formation of undesired needle‐like β‐intermetallic compounds (Al5FeSi). It is noted that both higher alloy Cr content and cooling rate induce refinement in the dendrite arm spacing, and improvement in both hardness and ultimate tensile strength when considering the alloys with identical Si content. The coefficient of friction slightly increases with increasing alloy Cr content and with coarsening of the microstructure. Correlations between the wear rate and secondary dendrite arm spacing are proposed, in which the wear rate decreases with decrease in the secondary dendrite arm spacing and increase in the alloy Cr content and hardness.

Effect of Alloying Elements on the Sr Modification of Al-Si Cast Alloys

Strontium-based modifier alloys are commonly adopted to modify the eutectic silicon in aluminum-silicon casting alloys by changing the silicon shape from an acicular to a spherical form. Usually, the modifier alloy necessary to properly change the silicon shape depends on the silicon content, but the alloying elements’ content may have an influence. The AlSr10 master alloy’s modifying effect was studied on four Al-Si alloys through the characterization of microstructural and mechanical properties (micro-hardness and impact tests). The experimental results obtained on gravity cast samples highlighted the interdependence in the modification of silicon between the Si content and the alloying elements. After modification, a higher microstructural homogeneity characterized by a reduction of up to 22.8% in the size of intermetallics was observed, with a generalized reduction in secondary dendritic arm spacing. The presence of iron-based polygonal-shaped intermetallics negatively affects Sr modification; coarser silicon particles tend to grow close to α-Fe. The presence of casting defects such as bifilm reduces Sr modification’s beneficial effects, and little increase in absorbed impact energy is observed in this work.

Understanding crystal structure and morphology evolution of Fe, Mn, Cr-containing phases in Al-Si cast alloy

As a common detrimental element in Al-Si cast alloy, Fe can be effectively removed by Fe-containing intermetallic separation in the alloy melt. However, the thermodynamic formation mechanism and growth morphology evolution of high separable Fe-containing intermetallic have not been investigated and clarified in detail until now. In this study, thermodynamic calculation, three-dimensional (3D) growth morphology and crystal structure were characterized to investigate the effect of Mn and Cr on morphology evolution, crystal structure and precipitation temperature of Fe-containing intermetallics. It is demonstrated that the addition of Mn and Cr can increase the precipitation temperatures of Fe-containing intermetallics in melt, and also result in the variation of crystal structures from monoclinic γ-AlFeSi to cubic α-AlFeMnCrSi phases. Moreover, the addition of Mn and Cr significantly changes the morphology of Fe-containing intermetallics from plate-like to cubic shapes. α-AlFeMnCrSi phase precipitated at high temperature exhibits the same structural basis as α-Al9Mn2Si2. The Fe-containing phase of cubic structure provides higher thermo stability which is in favor of its sufficient precipitation and separation.

Corrosion resistance of a novel ceria doped aluminum phosphate ceramic coating on cast Al-Si alloy by steam-assisted curing

A series of aluminum phosphate ceramic coating with the entrapped ceria (CeO2) nanoparticles, which is denoted APC, were constructed by steam-assisted curing method on cast Al-10Si alloy. The composition, structure and morphology of the coatings were investigated using FT-IR, XRD, XPS and SEM. Moreover, the corrosion properties of coatings were evaluated by the electrochemical tests. All the coatings were demonstrated to be homogeneous, compact on the substrate surface. The appropriate amount of CeO2 can effectively improve the corrosion resistance and durability of the coating. In addition, the formation and corrosion resistance mechanism of the coatings were studied in this work.

The Concept of Quality Index and Its Application for Al–Si Cast Alloys

The quality of aluminum–silicon casting alloys is considered to be a key factor in selecting an alloy for a particular engineering application. Deciding upon the right alloy quality thus involves reaching a suitable compromise between numerous factors so as to present the least possible risk with maximum performance in combination with adequate cost-effectiveness. Alloy composition, solidification rate, heat treatment procedures, casting defects, and such microstructural features as grain size and intermetallic phases, are all parameters which closely affect alloy quality since they also influence the mechanical properties of the casting. The development of the quality index concept and quality charts, in particular, in relation to their application to Al–Si casting alloys will be reviewed in this article. Although this paper covers only aluminum alloys, the methodology should also apply to other materials and alloys (iron and steels, Mg alloys, etc.) Caceres has established the scientific basis for constructing quality indices and plots, and this could be applied to other materials.

Stress Concentration on Eutectic Si Phase in Al-Si Cast Alloy by Means of Image-Based FE Simulation Based on High-Resolution Synchrotron Radiation Nano-Tomography

Stress Concentration on Eutectic Si Phase in Al-Si Cast Alloy by Means of Image-Based FE Simulation Based on High-Resolution Synchrotron Radiation Nano-Tomography

Effects of different nanoparticles additions on composition and properties of oxide layers formed by plasma electrolytic oxidation on cast Al-Si alloy

The effect of additions to the electrolyte of SiO2, Si3N4, Y2O3, WC and TiC nanoparticles (NPs) with a similar particle size on the structure, composition and properties of oxide layers formed by plasma electrolytic oxidation (PEO) on a cast Al-Si alloy 357.0 (7.5 wt % Si) was investigated. The oxide layers were studied by scanning electron and confocal laser microscopy (SEM and CLSM), energy dispersive X-ray microanalysis (EDXMA), X-ray diffraction analysis (XRD), and instrumental indentation. The thickness, roughness, microhardness and wear resistance of the oxide layers were determined. A complex positive effect of all types of particles added to the electrolyte on the hardness and wear resistance of the oxide layers has been established. The greatest positive effect was exerted by the addition of tungsten carbide NPs to the electrolyte – an increase in the average microhardness from 882 MPa in the base version to 1354 MPa and a decrease in the average reduced wear from 592 ng/(N*m) to 65 ng/(N*m), respectively.

Improvement of Al–Si Hypoeutectic Cast Alloy Properties by Forging with Grain Refiner and Modifier

In this paper, the microstructures and mechanical properties (i.e., impact, tensile and hardness) of four different hypoeutectic Al–Si cast alloys were studied before and after forging process. The effect of adding various grain refiners and grain modifiers on the properties were also studied. Results indicated that, in combination with grain refiner and modifier, the hypoeutectic Al–Si cast alloys have microstructures consisting of uniformly distributed α-Al dendrites, inter-dendritic network of fine eutectic silicon and fine precipitation of CuAl2 particles in the inter-dendritic area after 50% reduction in forging. The combined addition of grain refiner and modifier to the alloy demonstrated improved mechanical properties in as-cast condition as opposed to those alloyed with individual grain refiner or modifier. The improved mechanical properties of hypoeutectic Al–Si cast alloys were linked to reduced primary dendrites, uniform distribution of eutectic silicon and inter-dendritic precipitation of small CuAl2 particles after forging.

Study of Microstructural and Machining Characteristics of Hypereutectic Al-Si Alloys Using Wire-EDM for Photovoltaic Application

Aluminum-Silicon (Al-Si) alloys are extensively used in aerospace, automotive, thermal storage, and other engineering sectors because of their enhanced mechanical properties. Recently, Al-Si alloys are proved to be an efficient material for thermal storage during high and medium temperature storage applications. Hypereutectic Al-Si alloys are proved to be promising alloys due to their low coefficient of thermal expansion, low density, high wear, and corrosion resistance. In the present manuscript, an attempt is made to study the microstructural and machining characteristics of Al-Si alloys with a varying percentage of Silicon (16%, 20%, and 24%) in the alloy systems. Microstructural analysis was carried out on both the as-cast and heat-treated conditions through FESEM analysis. Further, the machinability studies of the alloy systems are studied by machining them using wire electric discharge machining (WEDM). It was observed that as cast Al-Si alloy has shown better machining characteristics than that of the heat-treated alloy. With the enhanced machining properties, the Al-Si alloy is well suited for the fabrication of structural parts of photovoltaic solar cells.

Development of High Corrosion- and Wear-Resistant Al-Si Alloy Coating on AZ80 Mg Alloy by Hot Extrusion

Mg alloys have been known as the lightest metal materials. However, their practical use is strictly limited due to their poor corrosion and wear resistances. To improve those resistances simultaneously, the present authors have fabricated an Al-Si alloy coating on a Mg alloy substrate by hot extrusion. The Al-Si alloy for coating material was prepared by powder metallurgy and casting processes. An AZ80 Mg alloy billet, a compacted Al-Si alloy plate or a cast Al-Si alloy plate, a die and rams were put in bottom of an extrusion container, and the Mg alloy and the Al-Si alloy were indirectly extruded together. By the hot extrusion, the Mg alloy was successfully coated with the Al-Si alloys prepared in both the powder metallurgy and the casting. The Al-Si alloy-coated Mg alloys showed a high corrosion resistance in a 1.0 mol/L HCl aqueous solution. Also, the wear resistance of the Mg alloy was significantly improved by the Al-Si alloy coating layers. The highest wear resistance was obtained with a cast Al-20 vol.%Si alloy coating layer. The coating improved the wear resistance by 50% compared with the AZ80 Mg alloy.

Study on the Microstructure, Mechanical Properties, and Erosive Wear Behavior of HVOF Sprayed Al2O3-15 wt.%TiO2 Coating with NiAl Interlayer on Al-Si Cast Alloy.

Alumina oxide coatings are widely used in many industrial applications to improve corrosion protection, wear and erosion resistances, and thermal insulation of metallic surfaces. The paper presents study of the microstructure, mechanical, and wear properties of HVOF (high velocity oxy-fuel process) sprayed of Al2O3-15 wt.% TiO2 coating with the NiAl interlayer on the surface of Al-Si alloy castings. The microstructure of Al2O3-15 wt.% TiO2/NiAl coating was characterized by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of coating with low porosity, compact structure, good adhesion to the substrate with typical lamellar structure composed of a solid phase consisting of compounds included in the coating material and their phase variations. For analysis of the adhesion of coatings to the substrate, the scratch test was applied. An assessment of the erosive wear resistance of coatings was also carried out, confirming the significant impact of the interlayer as well as the microstructure and phase composition of the oxide coating on the wear resistance of the tested coating system. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the Al2O3-15 wt.% TiO2/NiAl/Al-Si alloy as microhardness and erosion resistance of the coating. It was found that the introduction of the NiAl metallic interlayer significantly increased resistance to cracking and wear behavior in the studied system.

Investigation of the Foundry Properties of the Locally Available Sands for Metal Casting

Utilization of locally available sands for building moulds for sand casting will reduce the production cost and time as compared to procured sands. In the present study, the foundry properties of the locally available sands namely, mined silica river and beach sands have been investigated to check their suitability for metal casting. Different physical and mechanical tests were conducted on the chosen sand samples. Aluminium alloy was cast in all mould types and its cast properties such as volumetric porosity and surface roughness (SR) i.e. Ra value were determined for comparison. The foundry test results showed that the beach sand was the finest possessing highest grain fineness number (GFN) of 64 and the mined silica sand was the roughest, possessing lowest GFN of 44 among all sand samples. The pH value of all the sands was more than 7 which represents their good bonding ability with the binder. The mould’s permeability and strengths was found to decrease and increase with rise of 5–30% clay content in all cases. The mined silica sand mould demonstrated highest permeability in contrast to other sand moulds. The Al-Si alloy castings obtained from the mined sand mould exhibited minimum porosity with acceptable surface roughness.