Shape Casting: 5th International Symposium 2014

Current melting practices for Al alloys are in general unsatisfactory because it is clear that properties of Al alloy castings are not under control. In particular the variability of tensile ductility appears to indicate the great variability of oxide bifilm contents. A melting and casting procedure is outlined in which (i) the primary oxide skins from the surface of charge materials are first separated from the melt, followed by (ii) procedures for reducing the population of oxide bifilms in suspension from the interiors of charge materials, (iii) Hydrogen gas is reduced passively, avoiding potentially damaging bubbling techniques. (iv) Finally, techniques for the transfer of good quality metal into molds without re-introduction of damage are briefly mentioned.

Semi-solid process is expected as near net shape method with high quality. In this study, the semi-solid aluminum slurry was injected into a metallic mold with spiral shape cavity via some gates of several thicknesses. The effects of injection speed and gate thickness on the distribution of casting defects and density were investigated. Most of the casting defects appeared at the center of the specimen. The casting defects were generated most frequently on the tip of the spiral specimen. The amount of casting defects was decreased by semi-solid injection process than general high pressure die casting. The density of specimen made by the semi-solid injection process was approximately the same as high pressure die cast at near the gate, and increased in the other area.

Optimum casting designs are unreliable without consideration of the statistical and physical uncertainties in the casting process. In the present research, casting simulation is integrated with a general purpose reliability-based design optimization (RBDO) software tool previously developed at the University of Iowa. The RBDO methodology considers uncertainties in both the input variables as well as in the model itself. The output consists not only of a reliable optimum design but also of the knowledge of the confidence level in this design. An example is presented where the design of a riser is optimized while considering uncertainties in the fill level, riser diameter, and the riser pipe depth prediction. It is shown that the present reliability-based method provides a much different optimum design than a traditional deterministic approach.

High pressures applied to the castings during solidification mean that semi-solid castings tend to be prone to surface blistering during subsequent T6 heat treatment. It is believed that the blistering originates from subsurface defects present in the semi-solid castings, which expand when exposed to high temperatures during the solution heat treatment. Despite the significance of blistering to the commercial development of the semi-solid casting process, there have only been limited quantitative studies of the impact of process parameters on blistering. This paper, therefore, will report on a study to examine the impact of a number of process parameters including intensification pressure, plunger velocity and solid fraction of the feed material on the blistering of semi-solid castings during T6 heat treatment. The location and average size of blisters formed at each condition have been measured and related to the casting conditions.

This paper focuses on developing an innovative process route for Austempered Ductile Iron (ADI) casting production. The innovative process route introduces an integrated approach towards casting and heat treatment practices for the production of near-net shape light-weight ADI casting in a permanent mould. It is based on the fundamental correlation between the production parameters and its combined influences on the micro structure to get the desired mechanical properties and performance in ADI castings. Casting and heat treatment practices are implemented efficiently in a control manner using thermal analysis adaptive system (melt quality) and fluidized bed heat treatment facility (controlled and uniform heat treatment) respectively to optimize the foundry practices for ADI production. The influence of austempering time on the microstructural characteristics, mechanical properties, and strain hardening behaviour of ADI was studied. Optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were performed to correlate the mechanical properties with micro structural characteristics. It was observed that the mechanical properties of resulting ADI samples were influenced by the microstructural transformations and varied retained austenite volume fractions obtained due to different austempering time. The results indicate that the strain-hardening behaviour of the ADI material is influenced by the carbon content of retained austenite.

Swage casting, a new semisolid metal processing technology, has been developed in Balkan Center for Advanced Casting Technologies (BCACT) for manufacturing near-net shape components from leightweight metals. Components with one rotating axis such as a cylinder can be produced on a swage casting machine from molten metal in a one-step operation. The present study was undertaken to investigate the effect of intensive shearing action on the morphological evolution of as swage-cast A356 (AlSi7Mg0.3) alloy. Compared with conventional squeeze casting, the experimental results show that intensive melt stirring during swage casting, promotes the formation of net-globular and rosette-shaped grains.

Additive manufacturing is being used in a variety of ways to support the production of complex castings. Some of the common additive manufacturing processes include fused filament fabrication, vat photopolymerization, powder bed fusion, binder jetting, and material jetting. In this paper, the authors discuss the use of (i) binder jetting technology to fabricate sand molds for casting complex, cellular structures and (ii) fused filament fabrication & vat photopolymerization to produce complex investment casting patterns. Binder jetting of foundry sand molds allows the realization of cast structures that are impossible to mold using conventional methods. The structures are lightweight, multi-functional and may provide exceptional blast protection. With regards to investment casting, wax is currently the primary material used for producing expendable patterns due to a desirable combination of thermal expansion, thermal conductivity and melting point. However, wax is not a typical printed material. A variety of polymers are available for additive manufacturing and, as would be expected, only a few are suitable for use as expendable patterns for investment casting. The best polymers for use as expendable patterns for investment castings are PMMA, epoxy resin containing a reactive diluent and ABS.

The results of a student project to produce two housing halves for an engine dynamometer are presented in this paper. The filling systems were designed to minimize turbulence and damage to the metal. The results of small changes in the filling system design are discussed. A new method of using different parts of the filling system (rigging) to evaluate the results of quality improvement efforts is introduced.

This paper investigates the solidification of highly viscous energetic materials cast into a projectile. Active cooling and heating (ACH) control solidification technology as well as mechanical vibration (MV) are applied to achieve unidirectional solidification and to reduce cracks, gas pores, and shrinkage defects and to decrease the detrimental gap size between the projectile and the solidified energetic material. A comprehensive numerical model was developed to simulate the solidification processes during casting of energetic materials, as well as the resulting induced thermal stresses. The optimized design parameters of the proposed technologies are developed based on numerical modeling and experiment work.A detailed comparison between the latest experiments performed at the University of Alabama, Solidification Laboratory, obtained with electrical heating and water cooling and with and without mechanical vibration is provided in this paper. In these experiments, a special wax material (e.g., Chlorez 700S) that has similar thermo-physical properties with the IMX-104 explosive material was used. Experiments performed at the USARMY ARDEC using the IMX-104 explosive material with steam heating and water cooling are also presented in this paper. These experiments are being used to further validate the numerical model.

To describe the solute effect on grain refinement, the growth restriction factor (Q) in multicomponent multiphase Al alloys has been often evaluated using a simple summation of the Q values of the individual constituents taken from the binary alloy diagram. Such kind of evaluation can lead to mistakes, or completely fail when an intermetallic phase, even in a trace amount, solidifies prior to the primary α-Al. A more accurate method to evaluate growth restriction factor (Q _true ) from thermodynamic descriptions is to calculate the initial slope in the development of constitutional supercooling (ΔT) with the phase fraction of the growing solid phase (f _s ). In this contribution, ThermoCalc software (with TTA15 database) was used to evaluate the Q _true in a series of Al-Cu based alloys with Ti, Zr and Sc additions. This investigation demonstrates that thermodynamic-based alloy design can provide a significant tool to develop novel Al alloys.

The Controlled Diffusion Solidification (CDS) is an innovative casting technology that is being successfully employed in the near net shaped casting of Al based wrought alloys; specifically the 2xxx and 7xxx series. The novelty of the CDS technology is that it could mitigate the notable casting defect in conventional solidification of the Al wrought alloys, namely, hot tearing and enables the alloy to be cast into near net shaped components. This publication presents an overview of the phenomenological mechanism that lead to the non-dendritic morphology of the primary Al phase in the as-cast microstructure that facilitates a viable opportunity to cast the wrought alloys into high integrity and structural near net shaped castings. The salient mechanical properties of the cast component with AA7050 alloy in various heat treatment tempers will be presented along with micro structural characterization. Additionally, potential application for the technology to be adapted to various Al shaped casting processes will be explored and presented.

Aluminium and its alloys are prefer choice of automotive parts due to their low density and high strength ratios. These critical applications requires high quality castings to be produced. Melt quality can be measured by bifilm index using reduced pressure test. This index is a numerical indication of bifilm quantity of the melt. It has been shown that these bifilms affect many of the properties significantly. One of the limiting factor of casting methods is the fluidity of the liquid metal. The aim of the study is to investigate the effect of bifilms (i.e. melt quality) over the fluidity of A356 by using spiral test mould. Different mould temperatures were studied and it was found that as the bifilm index was increased, the scatter of the test results was increased.

Fluidity of alloys are typically carried out in a spiral test mould. Due to the variation of the results, several attempts have been made to optimise the test procedure. Pouring basin has been updated by addition of a stopper and using a defined quantity of melt to be poured. However, one of the discussed issues of the spiral test mould is its fixed size cavity where the liquid is transferred. Therefore, a mould was introduced by Campbell in which a single runner bar was used to feed different thickness sections. In this study, this mould design was used to investigate the effect of temperature (700oC, 725oC and 750oC) and modification (Ti grain refinement and Sr) on the fluidity of A356 alloy. The results were compared with the simulation (SolidCast) to optimise the characteristics of the alloy.

Feeding and microstructure of a test casting rigged with different feeder combinations was studied. Castings were examined and classified by soundness and microstructure. Subsequently the casting macro- and microstructure was analyzed to study how differences in solidification and segregation influence the soundness of different sections of the castings. Moreover, the microstructural changes due to variations in thermal gradients are classified, and the variations in the mushy zone described.The paper discusses how solidification and segregation influence porosity and microstructure of ductile iron castings. The goal is to enable metallurgists and foundry engineers to more directly target mushy zone development to prolong the possibility to feed through this section. Keeping smaller section open for an extended period will make it possible to use fewer or smaller feeders, with reduced energy consumption and cheaper products as a result.

A combination of an automated SEM/EDX analysis, a special 2D-3D converter of nodule size distribution, and adaptive thermal analysis were used for the study of heterogeneous nucleation in ductile iron. The special quenching technique was applied to increase probability to reveal non-metallic heterogeneous nuclei in small graphite nodules. Ternary diagrams were developed to compare statistics of oxide and sulfide compositions in graphite nodules and metal matrix. Thermodynamics of heterogeneous nucleation of graphite phase in Mg-treated cast iron is discussed based on the novel experimental data.

In aluminum gravity castings, the external and internal shrinkages (micro-porosity) are more prominent than those in ferrous castings. In order to understand the relationship between these two shrinkages during solidification, three castings with various tilting angles (i.e., 0°, 45° and 90° designated as H- T-, and S- castings respectively) were designed.Two pouring temperatures (700 and 760°C) were conducted in the real aluminum casting experiments. The volume change of external surface sinks was quantified by the reverse engineering scanning method, while that of internal porosities was measured by Archimedes method. Numerical models for simulating the shrinkages of aluminum alloy casting were suggested and validated by these experiments. The influence of tilting angle of castings was reported.A linear function between maximum micro-porosity and pore formation pressure in the modeling result was proposed to predict the negative pressure within castings during solidification. Two feeding (liquid and mass feeding) mechanisms of the solidification in the real aluminum casting were clarified by the modeling results.

Quasi-directionally solidified plates were sand cast using unmodified Al-xSi-yCu-0.1Mg-0.5Fe alloy with two Si (x = 4.5 or 9 mass%) and three Cu (y = 0, 1 or 4mass%) contents, and the size of the intermetallic phase particles (β-Al₅FeSi and Al₂Cu) assessed at constant secondary dendrite arm spacing (SDAS) using optical microscopy and back scattered electron images. Increasing the concentration of Si alone or in combination with Cu refined the β-Al₅FeSi platelets, whereas increasing Cu at constant Si shows an SDAS and Si level dependent effect.

In the Al-Si alloy-system, titanium, boron and strontium are very effective refining primary aluminum and eutectic silicon, thus enhancing casting and mechanical properties. In literature there are different statements which titanium and boron contents are the most effective for grain refining and optimal mechanical properties. In addition some studies showed an interaction between boron and strontium which would lead to a decreased modification of the eutectic silicon. To evaluate these contrary effects in detail, the influence of titanium and boron on setting, microstructure and mechanical properties of die-cast strontium-modified A356 are shown by systematically varying the titanium and boron contents in the present study. Titanium in combination with a low boron content (50 ppm) leads to the highest eutectic undercooling and maximum tensile strengths. By the use of 150 ppm boron in a titanium-free A356 melt the smallest grain size and highest elongation at fracture could be achieved.

In aluminium alloys, Cu and Mg are added in order to increase the strength. Obtained alloys are subjected to solution treated and precipitation hardening (T6) processing. Phases are formed with simultaneous diffusions of Cu and Mg in these alloys. The purpose of this study is the modelling of elements, which are in Al-Cu, Al-Mg and Al-Cu-Mg alloys, solution treatment times into alloys both one by one and in an interrelated way and their microstructural changings. Alloys are produced by pouring to both sand and metal mould. Then, these samples are subjected to solution treated and precipitation hardening processing in different temperatures and for different periods of time. Solution treated speeds of obtained samples are examined with microstructure and image analyses through metallographic examination and a model is designed. Microhardness analyses are also made. On the other hand, residual stress of alloys are examined with hardness, DSC and microstructure analyses.

There is growing evidence that the failure by cracking of nearly all solid metals, whether cast or wrought, is probably in most cases initiated by casting defects; entrained oxides known as bifilms which are the Griffith cracks necessary to initiate failure. Because bifilms are practically universally present in metals, the few examples of metals and alloys without bifilms, such as ductile iron, Hadfield Manganese Steel and Ni superalloy single crystals, appear to have unusually good properties, being unusually resistant to failure by cracking. Boron containing steels, and carbon steels deoxidised with CaSi might also be candidates. They indicate the potential for all metals and alloys if cast well. Current metallurgical thinking is required to recognize the current near-ubiquitous presence of bifilms in metals and the future casting technologies required for their avoidance. Uncracked and uncrackable metals having high strength, together with high ductility and toughness, should and could be the norm.

The measurement of melt quality of aluminum alloys have been a complex phenomenon. There exists various methods but the general experience show that they were slow, complicated or expensive for use on the foundry floor. In addition, these methods were not quantifiable. For the first time, bifilm index was proposed by the authors which give a numerical indication of the melt quality in millimeters as the total oxide length. Numerous studies were carried out to correlate this index with the mechanical properties. In this work, toughness measurements were made by using MatLab software. Alloy studied was 356 which were cast under various conditions (degassed and upgassed for 0.1, 0.2 and 0.4 cm3/100g Al) and the results were correlated with bifilm index.

Slower cooling and solidification rates tend to increase both the grain size and dendrite arm spacings (DAS) of conventional castings. Both grain size and DAS impact strength and ductility, and so heavy section castings generally have inferior mechanical properties than thin-walled castings. However, the primary phase of semi-solid castings is not produced during solidification in the mold, but instead is developed in the feed material. Therefore, the size of the primary phase is essentially independent of the solidification rate, and so the mechanical properties of semi-solid castings should be less sensitive to the wall thickness of the casting. This paper describes the results of a study to examine the impact of wall thickness on the microstructure, hardness and mechanical properties of semi-solid castings. Castings were produced at three thicknesses — 7.5 mm, 15 mm and 50 mm. Results are compared to literature data for conventional fully-liquid castings produced at similar section thicknesses.

The tensile and fatigue testing results of Staley Jr. et al. [Mater. Sci. Eng. A, v. 460–461 (2007) 324 and Mater. Sci. Eng. A, v. 465 (2007) 136] for A206-T71 castings were reanalyzed. The Weibull distributions for both elongation and fatigue life of castings that were hot isostatically pressed (HIPed) as well as those that received no processing (no-HIP) were correlated. Results indicate that significant improvements in fatigue performance are possible if pores old oxides are eliminated. Extrapolations of results and underlying mechanisms are also discussed.

A program within US CAR/US AMP-AMD (United States Car/United States Automotive Materials Partnership — Automotive Materials Division) Project entitled High Integrity Magnesium Automotive Components (HIMAC) was divided into several tasks, some involving the metallurgy of Magnesium casting alloys, and the rest to the production of an automotive control arm casting in AZ91 magnesium alloy by a variety of casting processes. Casting processes included: the Ablation Process, low pressure permanent mold (LPPM), squeeze casting (SC) and T-Mag. LPPM and SC are established processes, whereas the Ablation Process and T-Mag are relatively new processes in the early phases of being productionized. The performance of the castings from the various casting processes was compared. The Ablation Process was found to produce castings with the best combination of strength, ductility, reliability and X-ray soundness. Ablation fatigue resistance showed superior results. However, since ablated specimens did not fail in fatigue, Weibull quantitative results could not be ascertained, whereas, all other processes failure occurred.

The present paper uses the analytical cost estimation technique to estimate the variable cost of the CRIMSON process. In order to assess the performance of the CRIMSON process, the analytically estimated cost is compared with the conventional sand casting process cost. Because of the difficulty of data collection for analytical cost estimation, discrete event simulation method is employed to assist time based data collection. In order to cope with various input of the casting process, a comprehensive cost estimation tool was also developed to assist the cost estimation. It was found that the most expensive variable cost is the raw material cost, which can be 80% of the total variable cost. Furthermore, it is concluded that the CRIMSON process has less variable cost compared with the conventional sand casting process under most of the circumstances.

A review of Weibull mixtures in the mechanical properties of castings is provided. Two distinct scenarios which result in Weibull mixtures in the mechanical properties of castings are introduced: (i) multiple defect distributions that lead to failure by the same mechanism are present in the casting, and (ii) there are multiple failure mechanisms in effect regardless of the type and size of defects. These two scenarios are discussed in detail with examples from the literature.

The microstructure and mechanical properties of an automotive component die-cast by Swirled Enthalpy Equilibration Device process are analyzed. Two secondary aluminum alloys have been used, AlSi7Cu3Mg and AlSi9Cu3(Fe) alloys. The castings have been investigated by means of computer tomography to evaluate the concentration and distribution of casting defects, especially in the regions of thick wall thickness. Microstructural investigation has been carried out by means of optical microscope and image analysis technique. The results reveal a not uniform distribution of primary α-Al globules throughout the casting, with a solid fraction ranging from 48 to 58%, and eutectic segregation phenomena. The castings have been mapped in terms of mechanical properties and quality index. The variation of the mechanical properties reflects the presence of local casting defects and alloying segregation.

Casting durability may be assessed by several methods. In industrial powertrain castings engineering design is linked to the assessment of casting properties in particular high cycle fatigue performance. In the past porosity has been shown to be the most deleterious microstructural constituent in Al-Si cast alloys. Porosity is nucleated by oxide biflims and evolves during solidification due to segregated hydrogen gas and/or liquid feeding difficulties in the mushy zone during solidification. Porosity and oxide films have been reported to control casting durability as assessed through the fatigue staircase and calculated −3σ plots.The authors will show in this work that grain structure can also play a major role in terms of controlling fatigue life. Specifically the presence of columnar grains in non grain refined casting structures can lead to low and unpredictable fatigue lives. The mechanisms of fatigue failure due to grain structure are reviewed and the use of grain refiner (in-mold process) to improve fatigue performance and counteract undesirable structure are discussed.

Semi-solid forming methods are commercially used for both cast and wrought aluminium alloys. The main advantages are elimination of runners and feeders compare to the casting methods. In addition, near-net-shape parts can be produced. Non-dendritic structures are also known to have homogeneous microstructure. One of the methods of obtaining spherical microstructure is called SIMA (Strain Induced Melt Activated). In this work; this method was applied to AA2024 alloy. In order to obtain optimum spherical structure heat treatment was carried out 590, 610, and 630°C at certain time intervals. Then, moulds in the shape of a spanner with different thicknesses were used. Mould filling ability was characterized by means of microstructural analysis and using different mould temperatures. Tensile test samples were produced from the castings followed by T6 heat treatment and mechanical properties were investigated.

The assessment of the cleanness of liquid aluminum alloys has traditionally been viewed as difficult, but has been tackled by a number of techniques, all of which have been comparatively expensive and complicated. In the past the presence of entrained defects known as bifilms in metals has not been realised because they are often only a few molecules thick, and so remain invisible, or at best, difficult to detect. The reduced pressure test (RPT) is sensitive to the size and number of entrained oxides which appear to be the major defects affecting metal quality in terms of workability, mechanical properties and corrosion. In addition, the test is a confirmation of the fact that such oxides are double, and thus conveniently called ‘bifilms’. The RPT is a simple, low cost, but fundamentally appropriate technique for the assessment of (a) the number and (b) the size of bifilms in a melt. This paper outlines an initial draft procedure. Future users will be welcome to suggest improvements.

The prediction of misruns is challenging because flow and solidification have to be computed in a strongly coupled manner. Effects of surface tension, wetting angle and reduced melt flow due to the solidification must be modeled with high precision.To accomplish these requirements a finite-volume method with arbitrary polyhedral control volumes is used to solve flow and solidification in a strongly coupled manner. The Volume-of-Fluid approach is used to capture the phase separation between gas, melt and solid in connection with a High-Resolution Interface-Capturing scheme to gain sharp interfaces between phases. An additional source term in the momentum equation was implemented to model the resistance of the dendrite network to the melt flow.This methodology was applied to predict misruns in thin walled aluminum sand and TiAl centrifugal investment castings. Validation against casting trials using simplified geometries is followed by successful prediction of misruns in complex industrial applications.

Electromagnetic fields offer significant potential in metals processing. The ability to shape using the Lorentz force that arises from the interaction between the magnetic field and the current can be controlled. Since this is a containerless technique, contamination in the processed part may be reduced especially when using reactive metals. The force has a rotational component which induces melt motion which may lead to a refined micro structure. However, free surface motion has been demonstrated to be unstable, leading to difficulty in permanent feature creation. Simulations were generated to predict the force and temperature gradient in the melt and the coil. These results can be linked to the surface stability and shaping ability. Parameters were varied to enable design of a system that optimizes the maximum force and minimum heat input. By decoupling the forcing from the heating of the system, the widest range of operating conditions may be determined.

Liquid aluminium readily forms a surface oxide film, and during melting, casting and metal transfer operations double oxide film defects may be readily entrained into the liquid metal. Dissolved H is thought to diffuse into these defects and re-combine to form diatomic hydrogen molecules, leading to the formation of H porosity in the solid casting. However the diffusion of H into double oxide film defects may be considered unlikely as even thin Al oxide films have been reported to be effective barriers to the diffusion of H. In the experiments reported here, solid samples of commercial purity Al alloy were degassed by repeated use of a LECO hydrogen measurement device, then melted and exposed to an atmosphere of either oxygen or nitrogen. This created a surface containing Al₂O₃, or Al₂O₃ and AlN, respectively. When exposed to a H₂ gas atmosphere, the absorption of H was found to be greater in specimens containing AlN on the surface. The results suggest that AlN can form in cracks in an existing oxide layer and allowed greater diffusion of hydrogen when compared to samples with only alumina on their surface.

The microstructure evolution of a high-pressure die-cast AlSi9Cu3(Fe) alloy is studied over different Fe, Mn and Cr content. Fe-rich intermetallic phases were characterized by using optical microscope, image analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS). The results revealed that the amount of Fe-rich phases as well their size increase by increasing the elemental content. Needle-like particles appear in the alloy with higher Fe:Mn ratio, while coarse α-phases assume polygonal, stark-like or Chinese script morphology according to the Fe:Mn:Cr balance as revealed by EDS analysis. The 3D-SEM investigation suggests that both the polygonal and stark-like morphology can be associated to a rhombic dodecahedron structure. The morphology evolution of the Fe-bearing particles as a function of the chemical composition and casting process is proposed and discussed.

The effect of Fe and Sr on the evolution of the Fe intermetallic and eutectic phases in the Al-Si eutectic (Al-12.6 wt%Si) alloy was studied. Two different amounts of Sr (0.02 and 0.1 wt%) and three levels of Fe (0.5, 1 and 2 wt%) were introduced in the alloy; thermal analysis during solidification coupled with optical microscopy was carried out. It was observed, from the thermal data, that the nucleation temperature of the Fe intermetallic phase was not affected by the addition of Sr, but there is a significant variation in the heat balance during nucleation and growth of these phases during solidification. Additionally, the order of evolution of Al, Fe intermetallic phases and Si was significantly altered by the addition of Sr to the alloy. The analyses of the alloys showed that Fe intermetallic phase acted as nucleation sites for the Si phase while this was not the case in alloys with Sr addition. There is significant reduction in the size and alteration of the morphology of the Fe intermetallic phases when Sr was added to the alloy.

Predicting the misruns in thin-wall castings is required to produce lightweight high performance components. A general 1D heat transfer model for predicting the heat extraction of thin-wall castings is proposed. Temperature dependent properties calculated from a thermodynamic database are used to incorporate latent heat. A stopping criterion, related to a critical solid fraction, has been introduced to determine when the fluid solidifies and obstructs the flow. The model has been used to predict cast lengths in several conditions found in literature including die casting, sand casting and Ragone tests with good agreement to reported lengths. This model shows potential for use in 3D simulations of thin-wall castings.

The objective of this work was to study the corrosion behavior of dendritic diluted Al-Cu alloys, i.e., Al-1wt.%Cu and Al-4.5wt.%Cu (weight percent), directionally solidified vertically upward. During the solidification of the alloys, the phenomenon of columnar-to-equiaxed transition (CET) was obtained, and then, the properties are assessed according to the type of structure (columnar, equiaxed or CET) and composition. To determine the susceptibility to corrosion, working electrodes were prepared with different types of structures and cyclic potentiodynamic polarization measurements were conducted, as well as assays, electrochemical impedance spectroscopy (EIS) using solution of 3% NaCl at room temperature. It was observed that increasing the percentage of copper in the alloy, the corrosion potential moves to more anodic values. Impedance diagrams of the corrosion potential were obtained and then through a simulated equivalent circuit model. It is further noted that the resistance values decrease with increasing copper content in the alloys.