Conventional Casting Process Research Articles

Influence of Silicon Carbide/Graphite addition on properties of AA6082 reinforced composites

ABSTRACT AA6082 matrix hybrid composites reinforced with different weight percentages (wt. %) of (SiC + Gr) ceramic particulates by conventional stir casting process is manufactured. The weight percentage of ceramic powder is varied from 4 wt. % to 12 wt. % in a stage of 4 wt. %. The microstructures, physical properties such as density and porosity, as well as mechanical properties like hardness and tensile strength of the fabricated hybrid composites, are analysed. The optical micrographs reveal the uniform distribution of (SiC + Gr) ceramic particulates in the aluminium matrix. Density and porosity of hybrid composite increases from 2.69 to 2.75 g/cm3 and 0.37% to 1.23% with increase in weight percentage of (SiC + Gr) ceramic particulates in the aluminium matrix from 0 wt. % to 12 wt. % respectively. Both the hardness and ultimate tensile strength have enhanced from 52 to 84 VHN and 163 to 189 MPa, respectively, with a reduction in percentage elongation from 8.6 to 5.2 with rise in weight percentage of (SiC + Gr) ceramic particulates in the aluminium matrix from 0 wt. % to 12 wt. %, respectively.

Nanoparticles Reinforcement for the Improved Strength and High-Temperature Wear Resistance of Mn-Cr Steel

Nanotechnologies offer tremendous potential when it comes to modifying the microstructure of steel through the incorporation of nanoparticles. While typical production methods for metal-matrix composites are difficult and expensive, conventional casting routes suffer from inhomogeneity and agglomeration of the added nanoparticles. The aim of this study was to investigate the feasibility and possibilities of introducing nanosized particles into a steel matrix through a conventional casting process and to determine the effect of different nanoparticles and methods of incorporation on the strength, toughness, and high-temperature wear resistance of martensitic steel. The results show that also in the case of a conventional casting process, it is possible to obtain a homogeneous distribution of nanoparticles in the metal matrix, resulting in improved strength, maintained toughness, and up to five times better high-temperature wear resistance of the Mn-Cr steel. However, the rate of improvement greatly depends on the method and type of nanoparticles incorporation. The most promising results were observed for the combination of carbon nanotubes, oxide nanoparticles, and dispersant, sealed in a steel tube, with the dispersant providing the uniform distribution, the carbon nanotubes delivering the good toughness and the adhesive wear properties, and the oxide nanoparticles ensuring oxidation and abrasive wear resistance.

Micro-patterned 3D Si electrodes fabricated using an imprinting process for high-performance lithium-ion batteries

To overcome the volumetric expansion of Si used as an anode in lithium-ion batteries (LIBs), we propose 3D Si electrode structures formed on patterned Cu current collectors designed from metal molds fabricated using wire electrical discharge machining (WEDM). The line- and check-patterned Cu current collectors with microscale periods for LIBs are prepared using an imprinting technique with patterned metal molds fabricated using the WEDM process. The line- and check-patterned Si thin-film and powder-type electrodes as anodes are fabricated using radio frequency magnetron sputtering deposition method and conventional slurry casting process, respectively. The morphology of the Si electrodes before and after the cycling process is characterized using optical microscopy and scanning electron microscopy. The electrochemical properties of the Si electrodes are evaluated using a multi-channel battery tester and electrochemical impedance analyzer. In particular, the check-patterned Si electrodes exhibit relatively high-capacity and enhanced cycling performance due to the stress relief of the Si anode.

Structure and inverse magnetocaloric effect in Ni-Co-Mn-Sn(Si) Heusler alloys

In the presented work, a systematic study of crystal structure, microstructure, magneto-structural behavior and inverse magnetocaloric effect in the Ni44Co6Mn39Sn11-xSix (x = 1, 2 at.%) Heusler alloys, obtained by conventional casting and rapid solidification process, have been performed. All alloys, independently of the chemical composition, i.e. different addition of Si and fabrication process (melt-spinning and induction melting) were fully martensitic at ambient temperature. This was the case in spite of the large difference in the mean grain size of ribbons compared to bulk. Interestingly, the microstructure of ribbons consists of larger grains of about 5–20 μm in diameter with martensitic relief and smaller cells of about 1 μm. The crystal structure of both ribbons and bulk was identified as modulated six-layered (12 M) martensite with five additional spots between main reflections in the reciprocal space. The characteristic temperatures of the martensitic transformation were lower for melt-spun ribbons with respect to bulk. This may be connected with the grain refinement, internal stresses and high density of dislocations caused by rapid solidification process. Moreover, the addition of Si enhances the transformation temperatures. The calculated values of magnetic entropy change were higher for bulk alloys than ribbons.

Inclusion evolution in additive manufactured 316L stainless steel by laser metal deposition process

In laser metal deposition (LMD) process, meltpool oxidation is inevitable due to high working temperature, which results in finely dispersed non-metallic inclusions in the steel matrix. In this paper, characteristics of these inclusion, such as number density and mean radius, were controlled by means of changing process parameters, for instance, scan speed and laser power, using AISI 316L stainless steel powders. Subsequently, the yield stress of cast samples from each condition was measured in order to investigate the possibility of utilizing these inclusions in material strengthening. As oxygen contents varied from 306 ppm to 994 ppm, number densities of inclusion varied from 16,900/mm2 to 34,000/mm2. The yield stress of deposited material was proportional to inclusion number density ranging from 218 MPa to 269 MPa. Oxygen contents were governed by beam intensity and deoxidizer compositions in the powder, while faster scan speed gave smaller inclusion diameter due to shorter time for growth. The composition and viscosity of slag layer, which covered interface between superheated meltpool and atmosphere, brought in a large difference in oxidation kinetic. Compared with conventional casting process, a large number of inclusions were more finely distributed and possess smaller size, meaning that oxide metallurgy can be fully utilized in the LMD process.

Optimization of squeeze cast process parameters on mechanical properties of Al2O3/SiC reinforced hybrid metal matrix composites using taguchi technique

Squeeze casting is known to overcome the defects that incur during the conventional casting processes. The near-net shape manufacturing ability and potential to yield higher hardness are the capability of the squeeze casting provided technical parameters are accurately controlled. In this research, optimization technique for squeeze casting process parameter is established by Taguchi technique to explore the correlation among the hardness and tensile strength. Four different process parameters namely squeeze pressure, melt temperature, die temperature and holding time were selected to perform the experiments using L16 orthogonal array. The composites obtained for optimum cast conditions were squeeze pressure 100 MPa, holding time 30 s, melt temperature 750 °C and die temperature 100 °C exhibited better hardness and tensile strength. The identified process parameters provide a favorable condition for processing the alloys directly on the melt up to the time of complete solidification. The results indicate that there exists a strong correlation between hardness and tensile strength.

A comparative study of fabrication of sand casting mold using additive manufacturing and conventional process

In this study, two processes to fabricate casting mold, conventional sand casting process and additive manufacturing or 3D printing process, are comparatively investigated. The two processes were compared in terms of their weight saving, surface finish, design allowance, and fettling work. The results show that there are significant advantages in using additive manufacturing in the production of mold. The 3D printed molds provide substantial saving of sand used, design allowances, and fettling work. The mechanical properties of 3D printed molds are also higher than the conventional ones due to good bonding strength during 3D printing.

Comparative study of fatigue properties of Ti-6Al-4V specimens built by electron beam melting (EBM) and selective laser melting (SLM)

Electron Beam Melting (EBM) and Selective Laser Melting (SLM) are two of the most developed powder bed fusion based additive manufacturing processes. In this paper, fatigue properties of Ti-6Al-4V specimens built by EBM and SLM are compared. Several parameters are assessed: processes, manufacturing direction, surface roughness, HIP treatment. Fatigue properties are analyzed in relation with the crack initiation mechanisms identified on each specimen's post-mortem micrographs. Machined specimens show better fatigue properties as surface defects are removed. HIP treatment improves fatigue properties by decreasing the defects size. Small differences in lifetime are observed between horizontal and vertical building directions because of different defect shapes regarding the loading axis. Finally, EBM and SLM parts have approximately the same fatigue properties, which are equivalent to conventional casting processes.

A Numerical Simulation of Transport Phenomena During the Horizontal Single Belt Casting Process Using an Inclined Feeding System

Horizontal single belt casting (HSBC) has great potential to replace current conventional continuous casting (CCC) processes for sheet metal production, by directly casting 3 to 1 mm sheet for the automobile industry. In the present paper, two-dimensional mathematical models were developed to study transport phenomena, for the case of an inclined wall feeding system for a liquid aluminum wrought alloy (AA6111). Based on the commercial software ANSYS FLUENT 14.5 and user-defined functions, a two-layer turbulence model was used to examine the fluid flow emanating from a slot nozzle set above a water-cooled, high-speed, steel belt. The Volume of Fluid (VOF) method was used to predict the shape of the melt-air interface. A transformed coordinate system (x′, y′) was established in order to analyze the fluid flow on the inclined wall of the feeding system. The total pressure gauge gradient (∂ptotal/∂x) was used to describe the behavior of the melt film inside the slot nozzle of the head box. The modeling results show that during the melt film falling process, the total gauge pressure varies within the slot nozzle, which can decrease the stability of the falling film. The first impingement between the falling film and the inclined refractory wall of the feeding system gives rise to a local oscillation, and this influences the stability of the melt film moving downwards. At the rear meniscus position between the inclined wall and the moving belt, there is a clear vibration of the air-melt interface, together with a recirculation zone. The weak vibration of the air-melt interface could be induced by the periodic variation of the melt-air interface. Moreover, the formation of tiny air pockets is predicted. Finally, on the inclined wall of the feeding system, a suitable length of the transition area is needed to avoid over-acceleration of the melt film due to the force of gravity.

Microstructure and mechanical properties of Al-Si alloys processed by strain induced melt activation

Semi-solid metal processing (SSMP) is an effective near net shape forming processes that have many advantages over the conventional metal casting process. The strain induced melt activation (SIMA), one of the SSM processes, is adapted to produce Al-Si alloys with near globular microstructure. Among the cast alloys, Al-Si alloys are widely used in automotive applications owing to their high wear resistance, moderate strength to weight ratio and low thermal expansion coefficient. Conventionally cast Al-Si alloys have dendritic structure and contain defects such as porosity, blow holes, shrinkage etc. To overcome this defect, semi-solid metal processing is used to obtain globular structure with enhanced mechanical properties.In this investigation, the effects of silicon percentage on mechanical properties and microstructure of Al-Si alloys produced through SIMA process was investigated. Al-Si alloys containing 7%, 12% and 14% wt% Si were prepared through melting and casting route. The microstructure and mechanical properties of conventionally cast and modified SIMA processed Al-Si alloys were observed and evaluated. The SIMA processed samples show significantly higher properties than the samples prepared through conventional cast route. The UTS increased but percentage of elongation decreased with increasing Si wt %. The better combination of mechanical properties obtained when 60% deformed Al-7wt%Si alloy was isothermally hold at temperature 585°C for 30 min.

Microstructure and Tribological Characteristics of Strain-Induced Melt Activation (SIMA)-Processed Al–10Cu–Fe alloy

In the present study, the influence of synthesis methods, namely the conventional metal mould casting (MMC) and strain-induced melt activation (SIMA) processes, on the microstructure and tribological characteristics of Al–10Cu–Fe alloy has been studied. The alloy was prepared by melting the commercial purity aluminium and copper. The effect of holding time in semi-solid region on the microstructure of the alloy subjected to SIMA was studied. Microstructural characterization was performed using optical and scanning electron microscopy, while chemical segregation is investigated using energy-dispersive spectroscopy. Hardness and strength of the resulting alloy are measured using macroindentation and tensile testing, respectively. Near-spherical grains were achieved in the SIMA process with an average grain diameter varying from 44 to 67 µm for holding times ranging from 30 to 55 min. The wear properties of stirred MMC alloy which was subjected to SIMA process are considerably better than those of either conventional MMCs or unstirred MMC subjected to SIMA process. The 50% pre-deformation followed by intercritical annealing at 580 °C and 30 min holding time is the optimum parameters to obtain the wear properties of Al–10Cu–Fe alloy. The improved wear and mechanical properties of the alloy are discussed in the light of the microstructural features of SIMA-processed alloy and the nature of the worn surfaces.

Simple iterative procedure for the thermal–mechanical analysis of continuous casting processes, using the element-free Galerkin method

ABSTRACTThe present work has been conducted to develop a straightforward procedure for solving the thermal–mechanical problem in a conventional continuous casting (CC) process using the element free Galerkin method. The linear momentum balance equation has been developed on the basis of this global weak formulation. The model has been solved under a nodes-fixed mixed Eulerian–Lagrangian description to estimate the mechanical behavior of a round billet during the CC process in the mold region. The proposed approach is developed in a predictor–corrector scheme, which provides a solution involving simultaneously all the materials configuration downwards the mold without the requirement of a viscoplastic tangent operator. The results have revealed that this technique could be used successfully in the modeling of continuous casting thermal–mechanical problems.

Using Induction Melting to Make Lithium-Ion Battery Material

Abstract Lithium-ion batteries are an important enabling technology for electric vehicles. This article reports on a study in which an induction melting process was evaluated to produce LiFePO4 (LFP) ingots as well as granules from low-cost precursors. The melt casting process can provide the benefits of utilizing various precursors, rapid reaction kinetics, homogeneous liquid composition, and scale-up readiness. More importantly, this process also offers the possibility of lower-cost battery materials at a similar or better performance level as compared to solid state methods. If successful, melt synthesis of battery cathode material could offer a novel application of the conventional casting process.

EFFECT OF THIXOFORMING ON THE WEAR PROPERTIES OF AL-SI-CU ALUMINUM ALLOY

In this study a hypoeutectic Al-6Si-3Cu aluminium alloy was synthesized using two different routes: the thixoforming process and the conventional mould casting process. The microstructural features, hardness and wear behavior of thixoformed alloy have been evaluated and compared with that of as-cast alloy. Cooling slope method was used to produce the non-dendritic microstructure feedstock for thixoforming. Thixoforming was carried out at 50% liquid fraction. The dry sliding wear behaviour of the produced alloys was investigated under two loads; namely, 10 and 50 N and 1m/s sliding speed for 9 km sliding distance. The thixoformed alloy exhibited globular primary phase morphology with fine and uniform distributed Si and intermetallic particles. On the contrary, dendritic primary phase, coarse flaky silicon particles and segregated microstructure has been observed in conventional cast alloy. Thixoformed alloy exhibited improvement in the wear resistance in comparison to the conventional cast alloy, which may be attributed to the microstructural enhancement resulting in improved hardness. The thixoformed samples displayed lower volume loss of ~16.20 mm3 and ~42.40 mm3 at loads of 10 and 50 N respectively compared with that of conventional cast samples. On the basis of observations and analyses on the wear rates and worn surfaces, the wear mechanism of the alloys was dominantly controlled by abrasive, adhesive and minor delamination.

Microstructural evolution during semisolid processing of Al–Si–Cu alloy with different Mg contents

A series of Al–6Si–3Cu–(0.3–2)Mg alloys were produced by a conventional casting process. Cooling slope technique was employed to produce feedstocks before they were thixoformed at 50% liquid fraction. The effect of Mg on the microstructure of Al–Si–Cu aluminium alloys under as-cast and semisolid conditions was investigated. It was found that by adding Mg to Al–Si–Cu alloy, some of the Al2Cu phase and silicon were consumed to form Al5Cu2Mg3Si5 and Mg2Si phases. The needle-like β-Al5FeSi phase transformed to Chinese-script-like π-Al8Mg3FeSi6 with the addition of Mg. In the as-cast alloys, the primary α(Al) was dendritic, but as the Mg content increased, the phase became less dendritic. Moreover, the Mg addition considerably modified the size of the α(Al) phase, but it had no significant effect on the silicon morphology. In the thixoformed alloys, the microstructure showed a fine globular primary phase surrounded by uniformly distributed silicon and fragmented intermetallic phases. The eutectic silicon was modified from a flaky and acicular shape to fine fibrous particles. The effect of Mg on eutectic silicon during semisolid processing was evident. The primary Mg2Si particles were modified from big polygonal particles to become smaller and more globular, whereas the morphology of the Chinese-script-like π-Al8Mg3FeSi6 changed to a compact shape. The results also exhibit that as the Mg content in the A319 alloy increased, the hardness, yield strength and ultimate tensile strength of the thixoformed alloys significantly improved, but the elongation to fracture dropped.

Effects of Nano Particles on the Microstructure of LM 25 (A356) Alloy Manufactured by Squeeze Casting

Conventional casting process cannot produce parts as strong as forged parts. Also there are chances of many casting defects such as porosity, hot tears, shrinkage, pin holes, blow holes, mould shift flash, slag, short casting, when casting method is used for fabrication. Thus cast parts only have low mechanical properties. Recent trend is to use Squeeze Casting, which results in superior mechanical and casting properties. This technique is a hybrid metal forming process combining features of both casting and forging in one operation. This process is suitable for low melting alloys like iron and nickel with mechanical properties enhancement. Reduction in micro porosity in cast part and also reduction in machining. Historically, the series of LM were developed for high strength, corrosion resistance, and good machinability for many applications. In this study Squeeze Casting process has been used, since it has porosity free equiaxed grain components of LM 25 composition and cylindrical shaped castings were manufactured successfully by squeeze casting machine at high temperature and high pressure. The first part of the study is about the microstructure of the LM 25 Al-7 Si-0.3 Mg-0.5 Fe alloy. The casting products were made by addition of nano particles and without nano particles. The size of bar casted was by squeeze casting process. It was 260 mm*46mm (7 Pieces). Microstructure of Cast without squeeze and without stirrer, without squeeze and with stirrer, with squeeze and with stirrer Alloys was studied. The second part of the work was the heat treatment process of the finished product. Heat treatment process was conducted at 490○C and for the heat treated metals was quenched at 30○C (water) for the heat treated and unheated metal casting product were taken and microstructure were studied. The results were compared before and after the heat treatment process for addition of nano particles and without nano particles.

Fabrication and Microstructure Study of Aluminum Matrix Composites Reinforced with SiC and B<sub>4</sub>C Particulates

In the present paper aluminum matrix composites were fabricated using base material AA6082-T6. SiC and B4C particulates were used as reinforcement to obtain hybrid and non-hybrid composites through the conventional stir casting process. AA6082-T6/SiC composites with 5, 10, 15 and 20 wt % of SiC; AA6082-T6/B4C composites with 5, 10, 15 and 20 wt % of B4C and AA6082-T6/(SiC+B4C) hybrid composites with 5, 10, 15 and 20 wt % of (SiC+B4C) taking equal fraction of SiC and B4C were made and the microstructure study was carried out. X-Ray diffraction (XRD) patterns revels the presence of reinforcement within the matrix along with some other compounds. The microstructure of the fabricated composites was examined with the help of Scanning electron microscope (SEM) and the micrographs revealed that the dispersion of reinforced particles was reasonably uniform at all weight percentages.

A Preliminary Study on Bi-Layered Ceramic Electrolytes of Mixed Conductor and Proton Conductor

In this contribution, we present an experimental study of single-layered electrolyte with mixed ion and electron conducting ceramic material SDC (Sm0.2Ce0.8O2-x) and bi-layered electrolyte of the SDC layer with proton conducting ceramic material BCY (BaCe0.9Y0.1O3-x) to enhance the electrolyte performance. Anode supported cell structure was adopted and the button cells were fabricated through conventional tape casting, screen printing and high temperature sintering processes. It was found that the open circuit voltages of the bi-layered electrolyte cells were higher than that of single-layered SDC electrolyte cells. The bi-layered cells showed a decent performance in the temperature range of 500-650°C. Interaction between the two electrolyte materials occurred at high sintering temperature, which led to an increase in electrolyte resistance as well as electrode polarization values.

Heating System for Riser Size Minimizing in Sand Casting Process and Its Experimental Verification

In the conventional sand casting process, the size of the riser is made larger than that of the cavity (product part) in order for the molten metal in the riser to solidify at a later stage than the molten metal in the cavity. In this study, a continuous heating method is developed and applied to the riser, using a cylindrical heater, to minimize the size of the riser. A mold having four cavities is designed for casting turbine housings. The height and diameter of the riser are chosen to be 80 mm and 20 mm, respectively. Solidification analysis results, using the analysis program MAGMA soft for casting simulation, showed that when the heater is implemented, the riser is the last to solidify. However, without the heater, the riser solidifies before the cavity, thus causing the riser to function improperly. Moreover, misruns are generated in the casted product if the heater is not implemented, as opposed to the case of a solid product without any defects, with the heater attached in the riser.

Mechanical Properties of Magnesium Alloys Produced by the Heated Mold Continuous Casting Process

Abstract Investigation of the tensile and fatigue properties of cast magnesium alloys, created by the heated mold continuous casting process (HMC), was conducted. The mechanical properties of the Mg-HMC alloys were overall higher than those for the Mg alloys, made by the conventional gravity casting process (GC), and especially excellent mechanical properties were obtained for the Mg97Y2Zn1-HMC alloy. This was because of the fine-grained structure composed of the α-Mg phases with the interdendritic LPSO phase. Such mechanical properties were similar levels to those for conventional cast aluminum alloy (Al84.7Si10.5Cu2.5Fe1.3Zn1 alloys: ADC12), made by the GC process. Moreover, the tensile properties (σUTS and εf) and fatigue properties of the Mg97Y2Zn1-HMC alloy were about 1.5 times higher than that for the commercial Mg90Al9Zn1-GC alloy (AZ91). The high correlation rate between tensile properties and fatigue strength (endurance limit: σl) was obtained. With newly proposed etching technique, the residual stress in the Mg97Y2Zn1 alloy could be revealed, and it appeared that the high internal stress was severely accumulated in and around the long-period stacking-order phases (LPSO). This was made during the solidification process due to the different shrinkage rate between α-Mg and LPSO. In this etching technique, micro-cracks were observed on the sample surface, and amount of micro-cracks (density) could be a parameter to determine the severity of the internal stress, i.e., a large amount to micro-cracks is caused by the high internal stress.