Search

• Gd addition to the Mg-4Al-5RE alloys produced by various casting methods can refine the grains and modify the morphology of the acicular Al11RE3 phase to the short rod-like. • Gd addition increases the impact toughness due to the lower tendency of the modified second phases toward crack initiation. • The fine-grained HPDC alloys have an inconsistent strain rate sensitivity during the impact event. • The fine-grained HPDC alloys have excellent impact toughness but show an insufficient plastic deformation capacity. This work investigated the microstructure and impact behavior of Mg-4Al-5RE-xGd (RE represents La-Ce mischmetal; x = 0, 0.2, 0.7 wt.%) alloys cast by high-pressure die casting (HPDC), permanent mold casting (PMC), and sand casting (SC) techniques. The results indicated that with increasing Gd content, the grain sizes of the HPDC alloy had a slight change, but the grains of the PMC and SC alloys were significantly refined. Besides, the acicular Al 11 RE 3 phase was modified into the short-rod shape under the three casting conditions. The impact toughness of the studied alloy was mainly dominated by the absorbed energy during the crack initiation. With increasing Gd content, the impact toughness of the studied alloy monotonically increased due to the lower tendency of the modified second phase toward crack initiation. The impact stress was higher than the tensile stress, exhibiting a strain rate sensitivity for the mechanical response; however, the HPDC alloy had an inconsistent strain rate sensitivity during the impact event due to the transformation of the deformation mechanism from twinning to slip with increasing strain. Abundant dimples covered the fracture surface of the fine-grained HPDC alloys, indicating a typical ductile fracture. Nevertheless, due to the deficient {10 1 ¯ 2} twinning activity and the suppressed grain boundary sliding during the impact event, the HPDC alloys showed insufficient plastic deformation capacity. [ABSTRACT FROM AUTHOR]

Metal sand casting is widely recognized as the most common method for producing components due to its cost-effectiveness and resource availability. This method is particularly essential in leading markets such as China, the US, and India. Despite its advantages, the sandcasting process is complex, and influenced by numerous parameters. This study focuses on ASTM A487, a low alloy steel used for API 6A and API 6D steel valves in pressure services. It is crucial to manage cooling rates from the moment molten metal is poured until solidification and through subsequent heat treatment cycles. Experiments with both slow and rapid cooling rates were conducted to examine the impact on the microstructure and mechanical properties of the component. To prevent oxidation of alloy elements, melting at 1650 °C was performed in an Electric Furnace with Argon Oxygen Decarburization (EFAOD). Si particles were added during melting to prevent cracking and improve fluidity and feeding characteristics. The casting underwent heat treatment, including heating to austenitizing temperature, quenching, and tempering, to modify the microstructure and achieve the desired mechanical properties. Influence of Si was particularly notable in both slow and rapid cooling, affecting grain size. Optical microscopy was used to analyze microstructural changes, and mechanical properties were assessed through experimentation. Adding up to 1% Si resulted in improved outcomes, with increases in ultimate strength and hardness noted after quenching, and enhanced impact toughness observed post-tempering. Normalized specimens displayed typical microstructures indicative of the alloy's toughness. In summary, the microstructure and mechanical properties were superior in specimens subjected to rapid cooling and tempered heat treatment, compared to those that underwent slow cooling, in the context of low alloy steel. [ABSTRACT FROM AUTHOR]

The article discusses the influence of heat treatment and metal forming parameters on formability and the structure of the AZ91 cast magnesium alloy. The aim of the article is to determine the optimal parameters of homogenization and plastic deformation of sand castings made of the AZ91 alloy in order to improve their properties and structure. In this study, sand castings made from the AZ91 alloy were examined. In the first stage, the castings were homogenized at: 385 °C, 400 °C, 415 °C and 430 °C with argon as a shielding gas for 24 hours and then quenched. Subsequently the upsetting tests were conducted at 380 °C; 400 °C; 420 °C; 440 °C for two deformation values: e = 0.7 and e = 1.1. After upsetting, the samples were water- and air-cooled. At this stage, a visual assessment was made and samples without cracks were subjected supersaturation at 415 °C for 6 h, and artificial aging at 175 °C for 24 h. Vickers hardness tests and microstructure assessment were carried out, at individual stages of testing. Based on the results obtained from the upsetting, structure and hardness tests, the most favorable homogenisation and plastic deformation conditions were determined for AZ91 alloy sand castings. The best results are achieved by homogenizing sand castings at 415 °C for 24 h. Among the tested parameters for conducting metal forming processing in the range of 380-440 °C and deformation values: e = 0.7 and e = 1.1, forging of sand-cast AZ91 magnesium alloy at 420 °C and deformation of e = 0.7 with water cooling seems to be the most favourable. The final heat treatment applied after the deformation process consists of supersaturation at 415 °C for 6 hours water quenching as artificial aging at 175 °C for 24. This combination of heat and plastic treatment parameters of castings allows for improvement of the structure and properties of sand castings made of the AZ91 alloy. [ABSTRACT FROM AUTHOR]

The studied silicon bronze (CuSi3Zn3Mn1) is characterised by good strength and corrosion resistance due to the alloying elements that are present in it (Si, Zn, Mn, Fe). This study analysed the casting process in green sand moulding, gravity die casting, and centrifugal casting with a horizontal axis of rotation. The influences of Ni and Zr alloying additives as well as the casting technology that was used were evaluated on the alloy’s microstructure and mechanical properties. The results of the conducted research are presented in the form of the influence of the technology (GS, GZ, GM) and the content of the introduced alloy additives on the mechanical parameters (UTS, A10, and Proof Stress, BHN). The analysis of the tests that were carried out made it possible to determine which of the studied casting technologies had the best mechanical properties. Microstructure of metal poured into metal mould was finer than that which was cast into moulding compound. Mechanical properties of castings made in moulding compound were lower than those that were cast into metal moulds. Increased nickel content affected the BHN parameter.

Consistent lightweight construction in the area of vehicle manufacturing requires the increased use of multi-material combinations. This, in turn, requires an adaptation of standard joining techniques. In multi-material combinations, the importance of integral cast components, in particular, is increasing and poses additional technical challenges for the industry. One approach to solve these challenges is adaptable joining elements manufactured by a thermomechanical forming process. By applying an incremental and thermomechanical joining process, it is possible to react immediately and adapt the joining process inline to reduce the number of different joining elements. In the investigation described in this publication, cast plates made of the cast aluminium alloy EN AC-AlSi9 serve as joining partners, which are processed by sand casting. The joining process of hypoeutectic AlSi alloys is challenging as their brittle character leads to cracks in the joint during conventional mechanical joining. To solve this, the frictional heat of the novel joining process applied can provide a finer microstructure in the hypoeutectic AlSi9 cast alloy. In detail, its Si is finer-grained, resulting in higher ductility of the joint. This study reveals the thermomechanical joining suitability of a hypoeutectic cast aluminium alloy in combination with adaptively manufactured auxiliary joining elements. [ABSTRACT FROM AUTHOR]

In order to improve the ductility of commercial WE43 alloy and reduce its cost, a Mg-3Y-2Gd-1Nd-0.4Zr alloy with a low amount of rare earths was developed and prepared by sand casting with a differential pressure casting system. Its microstructure, mechanical properties and fracture behaviors in the as-cast, solution-treated and as-aged states were evaluated. It is found that the aged alloy exhibited excellent comprehensive mechanical properties owing to the fine dense plate-shaped β' precipitates formed on prismatic habits during aging at 200 °C for 192 hrs after solution-treated at 500 °C for 24 hrs. Its ultimate tensile strength, yield strength, and elongation at ambient temperature reach to 319 ± 10 MPa, 202 ± 2 MPa and 8.7 ± 0.3% as well as 230 ± 4 MPa, 155 ± 1 MPa and 16.0 ± 0.5% at 250 °C. The fracture mode of as-aged alloy was transferred from cleavage at room temperature to quasi-cleavage and ductile fracture at the test temperature 300 °C. The properties of large-scale components fabricated using the developed Mg-3Y-2Gd-1Nd-0.4Zr alloy are better than those of commercial WE43 alloy, suggesting that the new developed alloy is a good candidate to fabricate the large complex thin-walled components. [ABSTRACT FROM AUTHOR]

Multi-material designs (MMD) are more frequently used in the automotive industry. Hereby, the combination of different materials, metal sheets, or cast components, is mechanically joined, often by forming joining processes. The cast components mostly used are high-strength, age-hardenable aluminium alloys of the Al–Si system. Here, the low ductility of the AlSi alloys constitutes a challenge because their brittle nature causes cracks during the joining process. However, by using suitable solidification conditions, it is possible to achieve a microstructure with improved mechanical and joining properties. For this study, we used the twin-roll casting process (TRC) with water-cooled rollers to manufacture the hypoeutectic AlSi10Mg for the first time. Hereby, high solidification rates are realisable, which introduces a microstructure that is about four times finer than in the sand casting process. In particular, it is shown that a fine microstructure close to the modification with Na or Sr is achieved by the high solidification rate in the TRC process without using these elements. Based on this, the mechanical properties increase, and especially the ductility is enhanced. Subsequent joining investigations validate the positive influence of a high solidification rate since cracks in joints can be avoided. Finally, a microstructure-property-joint suitability correlation is presented. [ABSTRACT FROM AUTHOR]

The effect of additions of alloying elements (Mo and Ni), austempering time and thickness of the product section on the mechanical properties of industrial ductile iron of grade GGG-70 (EN-GJS-700-2) is studied. Standard keel blocks and crankshafts have been produced by static sand casting from unalloyed, alloyed with 0.2% Mo and 0.2% Mo + 0.6% Ni ductile iron. Austempering is carried out at 350 °C for 90, 120, 150, and 180 min in a salt bath. It is shown that the alloying has a significant effect on the ability of cast iron to austempering and its mechanical properties after heat treatment. Alloyed cast iron has the best combination of ultrahigh yield and tensile strength with high ductility. After austempering, crankshafts alloyed with 0.2% Mo + 0.6% Ni have a typical ductile iron ADI structure even in the thickest sections (58-mm-thick main bearing center) with a uniform hardness distribution. [ABSTRACT FROM AUTHOR]

This study aims at investigating the possibility of rolling and increasing both the tensile strength and the elongation of thin-wall non-alloy ductile cast iron with a composition of C = 3%, Si = 4.15%, Mg = 0.04%, Mn = 0.36%, and carbon equivalent (CE) of 4.39% through the improvement of microstructure using ablation casting compared to conventional sand casting. A barium containing post-inoculant (Si = 72–77%, Ba = 2.0–3.0%, Ca = 1.0–2.0%, Al = 0.8–1.5%, Fe = bal.) was employed as inoculant to produce thin-wall ductile cast iron castings. Specimens with initial thicknesses of 4.4 and 8.3 mm were hot rolled at 780 °C and 900 °C for ablation and conventional method, respectively. The rolling process on the specimens improved the mechanical properties significantly. The microstructure of the ablation specimens after rolling consisted of elongated graphite, ferrite encapsulating graphite, bainite and martensite, while the microstructure of the normal specimen after rolling consisted of elongated graphite, carbide, and martensite. The ablation specimens with thicknesses of 4.4 and 8.3 mm were subjected to strains of 58% and 78%, respectively, and the ultimate tensile strength values obtained were 1257 and 873 MPa, respectively. Conventional specimens were also subjected to strains of 34% and 58%, and the ultimate tensile strength values obtained were 948 and 745 MPa, respectively. Moreover, the highest elongation (16.3%) was reported for the 8.3-mm-thick specimen. The results show that rolling on thin-wall ductile cast iron castings improved the microstructure and increased the tensile properties of cast iron components. [ABSTRACT FROM AUTHOR]

The studied silicon bronze (CuSi3Zn3Mn1) is characterised by good strength and corrosion resistance due to the alloying elements that are present in it (Si, Zn, Mn, Fe). This study analysed the casting process in green sand moulding, gravity die casting, and centrifugal casting with a horizontal axis of rotation. The influences of Ni and Zr alloying additives as well as the casting technology that was used were evaluated on the alloy’s microstructure and mechanical properties. The results of the conducted research are presented in the form of the influence of the technology (GS, GZ, GM) and the content of the introduced alloy additives on the mechanical parameters (UTS, A10, and Proof Stress, BHN). The analysis of the tests that were carried out made it possible to determine which of the studied casting technologies had the best mechanical properties. Microstructure of metal poured into metal mould was finer than that which was cast into moulding compound. Mechanical properties of castings made in moulding compound were lower than those that were cast into metal moulds. Increased nickel content affected the BHN parameter. [ABSTRACT FROM AUTHOR]

AlSiMgMn alloy was made by the sand casting under vacuum (SCUV) process at an absolute pressure of 53 mbar and compared its microstructure and mechanical properties with the open sand-casting process. The properties of AlSiMgMn alloy are influenced by the shape and size of the distributed eutectic silicon particle and the iron intermetallic formed during the solidification. The detailed microstructure and mechanical properties of AlSiMgMn alloy made by open sand casting and SCUV were investigated as a function of Fe, Mn, and Mg content. The result shows that the SCUV process developed a Si-granular eutectic structure in sand-cast AlSiMgMn alloy that improves the tensile properties by evenly distributing stress around the hard particles. The α-Al15Si2(FeMn)3 (α-Fe) intermetallic was formed Chinese-script morphology in AlSiMgMn alloy made by open sand casting and SCUV process. β-Fe2SiAl12 (β-Fe) was formed a needle-like structure in open sand casting. Whereas SCUV, β-Fe was seen plate-like structure surrounded by α-Al. This geometrical transformation of β-Fe from the needle-like structure to the plate structure eliminates stress raisers and improves the mechanical properties, especially ultimate tensile strength and elongation by 8.88 and 23.37%, respectively. [ABSTRACT FROM AUTHOR]

Arbomex S.A. de C. V. is one of the largest worldwide manufacturers of ductile cast iron camshafts, produced by means of the phenolic urethane no-bake sand mold casting method and cold box by stack molding technology. As a result of the development of high-strength ADIs, low alloyed with vanadium, for camshaft manufacturing, previous results were published on the as-cast process and the austempering heat treatments applied to the camshafts. In the present work, camshafts of ADIs, low alloyed with 0.2 and 0.3 wt.% V, were produced at austempering temperatures of 265 and 305 °C. The performance of the new camshafts was evaluated by wear testing to ensure the function and durability of the camshafts by means of the block-on-ring wear test and a valve train system to evaluate the volume loss of material removed and the geometrical changes of the camshaft, respectively. The ADIs heat treated to 265 °C showed a microstructure constituted of fine ausferrite that aided in obtaining the highest wear resistance in the block-on ring wear test. No wear or pitting evidence was detected on the camshaft lobes and roller surfaces after the OEM test protocol during the electric spin ring test at low and high conditions for the ADI alloyed with 0.2 wt.% V heat treated at 265 °C. [ABSTRACT FROM AUTHOR]

To evaluate the enhanced erosion wear performance under acidic medium, a new high-vanadium–chromium alloy (HVCA) is designed and test samples produced by sand casting. The microstructure was analyzed by SEM, TEM and XRD. The erosion wear performance was tested in acidic medium designed by orthogonal test method. The factors affecting the erosion wear performance of HVCA are analyzed. The research results show that microstructure of HVCA is characterized by different carbides (M7C3, M23C6, VC, M2C) distributed in martensite and residual austenite. The hardness is 65.16 ± 0.2 HRC, and the impact toughness is 9.82 ± 0.12 J/cm2. H2SO4 concentration has the greatest influence on the erosion wear performance of HVCA, followed by the erosion wear angle. The maximum erosion wear performance of HVCA is 1.59 times that of HCCI. Compared with HCCI, HVCA has excellent erosion wear resistance because of its high hardness and toughness, a small amount of fracture and carbide shedding, and slight corrosion and wear interaction under erosion wear condition. [ABSTRACT FROM AUTHOR]

In this study, the ability to control the thickness and composition of surface alloyed layer on mild steel (produced by coating the surface of the mold with metal powders) has been demonstrated. The surface alloying process was conducted during lab-scale sand casting by coating the mold surfaces with slurries containing Ni, Cr, Fe-Si, and Fe-Mn as alloying powders. Two different compositions of surface alloying powders were tested for their level of enrichment and effect on the properties of Wrought Carbon Grade B (WCB) steel. The powder quantity per unit area of mold surface was varied to control the thickness of the surface alloyed (SA) layer between 1000 and 4000 microns; the thickness varied linearly with the amount of powder per unit area. The microstructure, composition, and phases of the alloyed layers were characterized for a few selected samples. The presence of austenite, ferrite, and limited chromium oxide was observed in the surface alloyed layers by x-ray diffraction (XRD). Limited testing of surface alloyed samples showed an increase in the hardness and corrosion resistance as compared to WCB steel substrate. These improved properties can lead to an increase in the life of the cast components with a minimal increase in the production cost. [ABSTRACT FROM AUTHOR]

The aim of the study was to select the optimal content of zirconium introduced as an alloying additive to obtain the best strength properties of Al-Si alloy. A technically important disadvantage is the tendency of silumins to form a coarse-grained structure that adversely affects the mechanical properties of castings. To improve the structure, modification processes and alloying additives are used, both of which can effectively refine the structure and thus increase the mechanical properties. According to the Hall-Petch relationship, the finer is the structure, the higher are the mechanical properties of the alloy. The proposed addition of zirconium as an alloying element has a beneficial effect on the structure and properties of silumins, inhibiting the grain growth. The starting material was an aluminium-silicon casting alloy designated as EN AC-AlSi9Mg (AK9). Zirconium (Zr) was added to the alloy in an amount of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight. From the modified alloy, after verification of the chemical composition, samples were cast into sand moulds based on a phenolic resin. The first step in the research was testing the casting properties of alloys with the addition of Zr (castability, density, porosity). In the next step, the effect of zirconium addition on the structure and mechanical properties of castings was determined. [ABSTRACT FROM AUTHOR]

Spheroidal graphite cast irons with 0–4 wt% aluminum addition fabricated by green sand casting were austenitized at 900 °C for 90 min and subsequently austempered at 300 °C for 60 min. The samples were subjected to dry sliding wear tests against Al2O3 balls under various conditions. Microstructural analysis showed that increasing Al decreased the acicular ferrite ratio and disrupted graphite nodularity. Accordingly, ultimate tensile strength (UTS) and hardness decreased while impact strength increased except for the 4 wt% Al-alloyed cast iron. The Al2O3 layer formed around graphite nodules could not be removed during the austempering and caused an increase in the mechanical strength of this sample. Sliding tests revealed that the wear resistance of the samples increased with sliding speed and decreased with applied load. Worn surfaces predominantly suffered from abrasion, adhesion, and delamination. Although lower Al addition increased wear losses, 4 wt% Al-alloyed cast iron showed the best wear resistance. [ABSTRACT FROM AUTHOR]

The results of studies on the effect that the type of binder and casting technology exert on the microstructure and properties of AlSi7Mg alloy castings are discussed in this paper. Comparative tests were carried out on three casting manufacturing technologies, i.e., conventional sand mould casting and cooling process, metal mould (die) casting, and sand mould casting with ablation breakdown of mould and cooling of castings. Moulds were made from four different sand mixtures with inorganic binders hardened by various technologies. The microstructure of test castings was examined at three different levels, i.e., in the upper part, central part, and lower part of each casting. The tensile test at room temperature was carried out in accordance with standards. The experimental results showed differences in the microstructure of castings. The differences resulted from changes in the crystallisation path due to the use of three different casting technologies, ensuring different rates of heat dissipation from castings; they were also due to the shape of castings. It has been shown that castings made by ablation technology are characterised by a high degree of the microstructure refinement (SDAS reduced by 18–30%), which gives higher strength properties than the properties of castings made in conventional sand moulds. Samples taken from castings made by the ablation technology in moulds with phosphate binder and microwave-hardened geopolymer binder were characterised by the mechanical properties comparable to gravity die castings. [ABSTRACT FROM AUTHOR]

The cylinder head is one of the most complex and concentrated load components of the engine, playing an important role in the safety and reliability of the engine. In this paper, the finite element method is used to simulate the casting and heat treatment process of cylinder head. The distribution characteristics of microstructure, shrinkage porosity defects as well as mechanical properties are analyzed, and the mechanical properties simulation results were verified by experimental data. The results show that the microstructure varies significantly at different regions and is related to local cooling rate. The shrinkage porosity defects are mainly distributed in the thick walls and thin–thick wall junctions, but the porosity value is small and the effect on the mechanical properties could be ignored. The mechanical properties of different cylinders are similar, but there are obvious differences at the top plate, force wall and bottom plate in each cylinder, with a maximum difference of 12%. The large discrepancies of microstructure, shrinkage porosity defects as well as mechanical properties in cylinder head are caused by the different local filling and cooling conditions in the casting process. [ABSTRACT FROM AUTHOR]

The primary objective of this investigation is to employ computational simulation analysis of casting to determine effective riser dimensions and eliminate shrinkage porosity in actual spheroidal graphite (SG) iron flywheel casting. A simulation software, Pro-CAST, is used to simulate the solidification process under varying process conditions (i.e., without a riser and with an effective dimension riser). The simulation results are then confirmed by a subsequent experiment using green sand casting. Additionally, a thorough investigation is conducted to determine the correlation between the shrinkage behavior and its morphological characteristics of the cast components. The simulation results infer that the un-optimized dimension of the riser causes the shrinkage porosity and void formation largely in the thicker section, due to the lower eutectic solidification time. However, when the dimension of the riser is optimized, this effect is mitigated simply by ensuring the eutectic solidification time is higher than the eutectic solidification of the thicker section; thus, the mold is completely filled with no shrinkage porosity or void formation. It is evident that there is a good agreement between simulation and experiment when comparing the resulting appearance of components in simulations and experiments. [ABSTRACT FROM AUTHOR]

In modern vehicle chassis, multi-material design is implemented to apply the appropriate material for each functionality. In spaceframe technology, both sheet metal and continuous cast are joined to castings at the nodal points of the chassis. Since resistance spot welding is not an option when different materials are joined, research is focusing on mechanical joining methods for multi-material designs. To reduce weight and achieve the required strength, hardenable cast aluminium alloys of the AlSi-system are widely used. Thus, 85–90% of aluminium castings in the automotive industry are comprised of the AlSi-system. Due to the limited weldability, mechanical joining is a suitable process. For this application, various optimisation strategies are required to produce a crack-free joint, as the brittle character of the AlSi alloy poses a challenge. Thus, adapted castings with appropriate ductility are needed. Hence, in this study, the age-hardenable cast aluminium alloy AlSi10Mg is investigated regarding the correlation of the different thicknesses, the microstructural characteristics as well as the resulting mechanical properties. A variation of the thicknesses leads to different solidification rates, which in turn affect the microstructure formation and are decisive for the mechanical properties of the casting as well as the joinability. For the investigation, plates with thicknesses from 2.0 to 4.0 mm, each differing by 0.5 mm, are produced via sand casting. Hence, the overall aim is to evaluate the joinability of AlSi10Mg and derive conclusions concerning the microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the tensile properties and microstructure of Al-Cu alloy casting with a dimension of ∅500 mm × 700 mm and a 5mm-thick wall at room temperature and 200°C. The results indicated that the strength and elongation of Al-Cu alloy casting at room temperature were excellent, exceeding 425 MPa and 8%, respectively. Such a good performance was attributed to the tiny equiaxed grains. However, the occurrence of acicular θ phase distributed around the α-Al matrix grains was disadvantageous to strength and especially to elongation. Moreover, no dynamic recrystallization was observed in the tensile tests at 200°C. Besides, numerous dimples were found in the fracture morphology, which were beneficial to the elongation. [ABSTRACT FROM AUTHOR]

Research published in open literature on ablation casting has been mainly experimental. Modeling of this innovative technology is scarce. This article describes an initial attempt in modeling ablation casting process. Material properties and boundary conditions were defined for calculating cooling curves and microstructural length scales in A356 alloy castings made using sand casting and ablation casting processes. Model predictions were compared with published data on cooling curves and solidification times in an A356 alloy casting. The validated model was then used to predict unique solidification features associated with the ablation casting process, including the eutectic solidification time, shrinkage porosity formation, eutectic front morphology, the advancing rates of the eutectic front and the associated eutectic silicon morphology. Simulation results indicate that the progressive advancing ablation cooling is capable of reducing secondary dendrite arm spacing, modifying the eutectic silicon phase owing to the water quench effect, and eliminating shrinkage porosity using much smaller risers than usual if the ablation is correctly driven towards the risers. [ABSTRACT FROM AUTHOR]

The sand castings of Mg–Y–RE–Zr series alloys are widely utilized in the large scales and complex shapes in the aerospace industry, as a result of which there are always some cast defects in the products. In this study, the feasibility of repair welding of sand-cast Mg–4Y–3RE–0.5Zr alloy by tungsten inert gas (TIG) welding was scrutinized with different welding currents from 150 to 210 A. The results indicated that defect-free repaired joints with good appearance could be acquired at 170 and 190 A. Interestingly, the grain size of the fusion zone (FZ) was refined initially and then increased with the linear increment of welding current. Because at the higher heat inputs, although the cooling rate of the molten pool was reduced, substantial constitutional supercooling for the grain refinement was attained after the Zr particles were transformed into Zr solutes. The tensile strength of the repaired joint at 170 A was 195 MPa with the maximum joint efficiency of 87.8%, and the elongation reached to 124.4% of the sand-cast base material (BM). However, serious grain coarsening and continuous eutectic structures generated in heat-affected zone (HAZ) above 190 A resulted in the weakening of the joint due to the brittle intergranular fracture. [ABSTRACT FROM AUTHOR]

In this research, the effects of cooling rate on the microstructure and mechanical properties of 5182 aluminum alloy were investigated. Two plates were cast using conventional and ablation green sand mold casting processes and microstructure, casting defects, tensile properties, and hardness of these two castings were compared to each other. In the ablation casting, water spraying onto the mold was started immediately after filling the mold. In the ablation casting compared to the conventional casting following results were obtained: SDAS decreased from 70 to 41 µm. The eutectic phases were modified from coarse and lamellar morphology to fine and divorced morphology. The porosity content decreased significantly from 9.3 to 1.8%. The yield and ultimate tensile strengths increased from 153 and 188 MPa to 163 and 259 MPa, respectively, while the elongation increased from 2.3 to 12% and the hardness remains unaffected. [ABSTRACT FROM AUTHOR]

Ablation casting is an emerging sand casting technology that achieves high cooling rates in a casting during its solidification, especially its eutectic solidification of the metal, resulting in an extremely fine eutectic microstructure, reduced levels of defect, and enhanced mechanical properties of the casting. The technology is creating extensive interest in the industry for its capability in producing castings with high mechanical properties and internal integrity. However, scientific research lags behind the industrial applications of this new technology. There is a lack of scientific understanding on the solidification features of the castings made using ablation casting. Experimental data on the microstructural length scales seem inconsistent. This article aims at interpreting the experimental data available in the literature by considering the solidification characteristics of ablation casting. The paper also discusses certain research needs to further exploring the potential of the ablation casting process. [ABSTRACT FROM AUTHOR]

Casting is one method of making metal components that are widely used in industry and up to date. The sand casting method is used due to its simplicity, ease of operation, and low cost. In addition, the casting method can produce cast products in various sizes and is well-suited for mass production. However, the disadvantage of casting, especially gravity casting, is that it has poor physical and mechanical properties. Tin bronze Cu20%wt.Sn is melted in a furnace, then poured at a temperature of 1100°C into a sand mold. The cast product is a rod with 400 mm in length, 10 mm in thickness, and 10 mm in width. The heat treatment mechanism is carried out by reheating the cast specimen at a temperature of 650°C, holding it for 4 hours, and then rapid cooling. The specimens were observed microstructure, density, and mechanical properties include tensile strength and bending strength. The results showed that there was a phase change from α + δ to α + β phase, an increase in density as a result of a decrease in porosity and a coarse grain to a fine grain. In addition, the tensile strength and bending strength of the Cu20wt.%Sn alloy were increased and resulted in a more ductile alloy through post-cast heat treatment. [ABSTRACT FROM AUTHOR]

Semisolid casting using the cooling slope plate method (CSP) is known to refine the microstructure of hypereutectic aluminum alloys and enhance their mechanical properties. The current research investigates the combined effect of casting using the CSP and mechanical vibration of the mold on microstructure and wear behavior of A390 alloy. After pouring the alloy on the CSP, the mold (sand/metallic) was vibrated mechanically at 50 Hz during filling and up to solidification. Conventional casting with the same mold vibration conditions was also done for comparison. During CSP casting with mechanical vibration of the mold, the crystal nucleus multiplication inhibits the grain growth, and the dendrite break-up takes place simultaneously, leading to refinement of the microstructure. The double effect of the shear force by melt flow and vibrational turbulence is responsible for fragmentation of the particles. This finding was more pronounced in case of using the sand mold. The quantitative measurements showed that the size of primary Si reduced from ~ 184 μm for the conventional casting in the sand mold without vibration to ~ 70 μm when the mold was vibrated and from ~ 30 μm in case of CSP down to ~ 20 μm when CSP was followed by mechanical vibration of the mold. However, applying the mechanical vibration after CSP in case of the metallic mold increased the size of primary Si from ~ 21 to 36 μm. Accordingly, the improvement in the hardness and wear resistance of the CSP samples due to vibration was more significant in case of using the sand mold. [ABSTRACT FROM AUTHOR]

The effect of aluminum (0, 2, 4, and 6 wt. %) and copper (0, 2, 4, and 6 wt. %) on graphite morphology, microstructure and compressive behavior of ductile iron specimens manufactured by sand casting technique were investigated. The graphite morphology and microstructure were evaluated using optical microscopy (OM) and scanning electron microscopy (SEM) equipped image processing software. To study the mechanical properties, the compression test was conducted on the ductile iron specimens. The results indicated that the surface fraction and nodule count of graphite decreased when the amount of aluminum increased from 0 to 2 wt. % and after that from 2 to 6 wt. %. In addition, the nodularity of graphite increased with the increment of the aluminum amounts. By adding the amount of copper, the surface fraction and nodule count of graphite increased and nodularity of graphite decreased. The addition of aluminum and copper decreased the surface fraction of ferrite and increased the surface fraction of pearlite in the microstructure. By increasing the amounts of aluminum and copper, compressive stress vs. strain curves were shifted upwards, and modulus of elasticity, yield strength, maximum compressive stress, and fracture strain improved. In comparison with copper, aluminum had a greater influence on the mechanical properties of ductile iron. [ABSTRACT FROM AUTHOR]

Samples of ductile iron alloyed with 0.88 % Ni with a nodule count of 606, 523, and 290 nod/mm2 were obtained from sand cast plates of different thickness in the range from 8.46 to 25.4 mm. The effect of the nodule count was evaluated during the austempering process held at 285 °C and austempering times of 15, 30, 45, 60, 70, and 90 min. The volume fraction of high carbon austenite increased when the nodule count increased, however, the carbon content of the high carbon austenite kept almost constant. The process window was narrow, requiring a lower austempering time when the nodule count increased. The combination of a higher nodule count and low austempering temperature allowed obtaining a fine ausferritic microstructure which led to higher Brinell hardness and tensile strength. The process window was determined by XRD measurements and it was in good agreement with the microstructural and hardness evolution as the austempering time increased. [ABSTRACT FROM AUTHOR]

In this study, the sintering behaviour and densifications of chamotte refractories that were produced by incorporation of 4140 precision casting sand waste at different ratios are investigated. Thermal properties are examined using thermogravimetry and differential scanning calorimetry thermal analysis methods. Open porosities and densities of refractories have been determined using Archimedes principles according to ASTM C20. The chemical analysis of raw material and phase analysis of refractories, and also chamotte raw material and sintered chamotte material at 1723 K, are obtained by X-ray fluorescence and X-ray diffraction, respectively. In addition, the changes in microstructure are characterized using a scanning electron microscope. According to the results, chamotte refractory that was produced by 10% 4140 precision casting sand waste has the highest density and lowest open porosity due to the smallest grain size after sintering compared with those of pure (C0) refractory and chamotte refractory with the addition of 20% 4140 precision casting sand waste. [ABSTRACT FROM AUTHOR]

In this paper, the hot formability of 7075 aluminum alloy sand and permanent casting ingots were verified. The experiment was carried out by using casting, heat treatment (homogenization) of ingots and conducting isothermal compression tests at temperatures of 420-500°C. The effect of the forming temperature on the microstructure, the tendency for crack formation and hardness were determined. The results show that ingots in the as-cast state have a dendritic network structure rich in the second phase precipitation on the grain boundaries. After the homogenization process, the microstructure is significantly more balanced. The forming process at 420-480°C of sand casts leads to significant grain elongation and crack formation, mainly at the grain boundaries. Raising the forming temperature to 480-500°C leads to a reduction in the occurrence of cracks. On the other hand, permanent mold castings do not reveal cracks during deformation in the temperature range 420-480°C. [ABSTRACT FROM AUTHOR]

This investigation is focused on the corrosion evaluation of an as-cast Al-Si alloy, obtained by two different casting methods: traditional sand casting and three-printing casting, using a binder jetted mold. The experimental results are discussed in terms of chemical composition, microstructure, hardness, and corrosion behavior of two different casting parts. The microstructure and composition of the sample before and after the corrosion tests was analyzed using light microscopy (OM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (DRX). The corrosion of the two processed castings was analyzed using anodic polarization (PA) test and electrochemical impedance spectroscopy (EIS) in an aerated solution of 3.5% by weight NaCl, similar to the seawater environment. After the corrosion process, the samples were analyzed by inductively coupled plasma/optical emission spectrometry (ICP/OES); the composition was used to determine the chloride solution after immersion times. The sample processed by binder jetting mold showed higher corrosion resistance with nobler potentials, lower corrosion densities, higher polarization resistance, and more stable passive layers than the sample processed by sand casting. This improvement of corrosion resistance could be related to the presence of coarse silicon particles, which decrease of cathodic/anodic ratio and the number of micro-galvanic couples, and the lower amount of intermetallic β Al-Fe-Si phase observed in cast alloy solidified in binder jetting mold.

Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials. As weight reduction is desired, these cast components are usually made from high-strength aluminium alloys of the Al-Si (Mn, Mg) system, which have limited weldability. The mechanical joinability of the cast components depends on their ductility, which is influenced by the microstructure. High-strength cast aluminium alloys have relatively low ductility, which leads to cracking of the joints. This limits the range of applications for cast aluminium alloys. In this study, an aluminium alloy of the Al-Si system AlSi9 is used to investigate relationships between solidification conditions during the sand casting process, microstructure, mechanical properties, and joinability. The demonstrator is a stepped plate with a minimum thickness of 2.0 mm and a maximum thickness of 4.0 mm, whereas the thickness difference between neighbour steps amounts to 0.5 mm. During casting trials, the solidification rates for different plate steps were measured. The microscopic investigations reveal a correlation between solidification rates and microstructure parameters such as secondary dendrite arm spacing. Furthermore, mechanical properties and the mechanical joinability are investigated.

This study compares the microstructures and hardness of an AlSi10.6CuMg alloy obtained by sand casting and high pressure die casting (HPDC). The results show that the morphology of HPDC dendrites was not uniformly distributed as in sand casting. HPDC refines the morphology of intermetallics and produces a modification of eutectic silicon. Chinese-script is the dominant iron intermetallic in sand casting, while primary polyhedral and secondary proeutectic particles are dominant in HPDC. The results of the X-ray diffraction show the presence of high residual stresses in the HPDC. Deep etching for HPDC samples reveals θ-Al2Cu phases in very thin compact dendrites. No evidence of twin plane re-entrant edge assistance was found in the growth of primary silicon. The primary silicon plate-like becomes unstable in HPDC, resulting in smooth and rounded outer surfaces. Hardness of HPDC alloy was about 11% higher than that of sand casting alloy. [ABSTRACT FROM AUTHOR]

This study presents a systematic framework for reducing shrinkage porosity in high-performance steel castings, based on a simulation-driven optimisation process coupled to micro- and macrostructural evaluation of the castings. For the test case, the macro- and microstructural investigation of a Class 300 gate valve body, based on the ASME B16.34 standard and made from A216 WCB cast steel, using X-ray computed tomography and scanning electron microscopy, was presented in Part 1: Analysis, Techniques and Experimental Approach. This forms the basis for introducing appropriate design and process improvement measures to reduce shrinkage porosity severity levels, based on parameters that influence shrinkage porosity formation, particularly in terms of temperature gradient and solidification rate. Based on the improved design, and using a patternless sand mould manufacturing technology, a trial casting of the valve body was produced, showing a significant improvement in shrinkage porosity levels. [ABSTRACT FROM AUTHOR]

Permanent mold casting of ductile iron is an environmentally friendly alternative to sand mold casting. The high cooling rate leads to a homogeneous microstructure with low grain size, but can also lead to cementite formation. In the work presented, the as-cast microstructure of solid solution-strengthened ductile iron (SSDI) cast in permanent mold made of gray iron is analyzed. The high silicon content in SSDI decreases chilling tendency and promotes the formation of ferrite. Silicon contents in the range 3.2-4.3 wt% and mold preheating temperatures in the range 300-450 °C were analyzed for section thicknesses of 10, 20 and 30 mm. Solidification time and cooling rate at the casting sections analyzed were measured. The results show that an as-cast microstructure free from carbides is achieved in sections of 20 and 30 mm for all castings analyzed, whereas for 10 mm a partial chilled microstructure is produced. As expected, the pearlite content decreases with increasing silicon content and increasing preheating temperature. A higher cooling rate increases eutectoid undercooling and thus promotes pearlite formation. From the experiments carried out, a quantitative correlation is deduced for the pearlite content as a function of eutectoid undercooling and Si content. The nodule count is approximated as a linear dependency on solidification time. [ABSTRACT FROM AUTHOR]

Aluminium alloys are characterized by a low density, acceptable mechanical properties and good technological properties. This unique connection of features made aluminium alloys perfect structural material for the transportation industry. Also, due to their good electrical conductivity they also found application in energy production industry. High mechanical properties and electrical conductivity of the Al-Si alloys with Mg addition may be achieved by heat treatment. However, the highest mechanical properties are achieved in the early stages of age hardening - due to precipitation of coherent phases, while high electrical conductivity may be achieved only by prolonged aging, during precipitation of semi-coherent or fully noncoherent, coarse phases. Carefully heat treated AlSi7Mg alloy may exhibit both fairly high electrical conductivity and slightly increased mechanical properties. The following article present results of the research of influence of heat treatment on the properties and microstructure of sand cast AlSi7Mg alloy. Microstructure observations were performed using light microscopy, scanning electron and scanning-transmission electron microscopy. Hardness and electrical conductivity of the AlSi7Mg alloy were investigated both in as-cast condition and after heat treatment. Maximum hardness of the alloy is achieved after solutioning at 540°C for 8h, followed by 72h of aging at 150°C, while maximal electrical conductivity after solutioning at 540°C for 48h, followed by 96h of aging at 180°C. Increase of the electrical conductivity is attributed to increasing distance between Si crystals and precipitation of semi coherent phases.

The silicon carbide particle reinforced aluminum matrix composites are expected to have many applications in aerospace, aircraft, automobile and electronic industries. Aluminium Silicon Carbide (Al-SiC) is also used for Advanced Microelectronic Packages. In this study, effect of different weight percentage of strontium on microstructure and mechanical properties of Al-SiC composite and Al-12Si (LM6) was investigated. In this research, scanning electron microscope equipped with EDS was used to define how modifier effect on microstructure. To fabricate Al-SiC composite, 10 wt% silicon carbide and different percentages (0.02, 0.5) Wt % of Al-10Sr was added to Al-11.6Si (LM6) by using vortex method for mixing the particles. The influence of adding different amount of Al-10Sr (0.01, 0.02, 0.5) Wt% on mechanical behavior of aluminum was also examined. The results found that UTS for aluminum increased by adding SiC and Sr. It was observed that the tensile for the composite did not increase dramatically. It was concluded the weak interface between particles and matrix, decreased the UTS. On the other hand strong interface between particles or fibers in the matrix showed high stiffness and strength but typically a low resistance to fracture. [ABSTRACT FROM AUTHOR]