Molten Aluminum Alloy Research Articles

Evolution of the Microstructure of Intermetallic Compounds Formed on Mild Steel During Hot Dipping in Molten Aluminum Alloy Baths

Hot-dip aluminum coating technique has been applied to improve the high-temperature oxidation resistance of steels. This method is adopted widely due to the low cost and good performance. The purpose of this paper is to study the formation of intermetallic layers during the hot dipping of mild steel into a molten aluminum bath. Mild steel specimens were immersed into molten aluminum alloy baths at 750 °C for 1 h, 2 h and 3 h. Intermetallic compounds were analyzed by optical microscope, scanning electron microscope coupled with energy-dispersive spectroscopy and X-ray diffraction analysis. This study was completed by microhardness testing. The results showed that the hot-dip aluminized layer was divided into an outer pure aluminum or aluminum–silicon topcoat and an intermetallic layer. In the bath of pure aluminum, the intermetallic layer was the thickest and consisted of an outer FeAl3 layer and an inner Fe2Al5 layer adjacent to the steel substrate with tongue-/finger-like morphology, while in the Al–Si alloy bath, the thickness of the intermetallic layer decreased substantially and the interface intermetallic/steel substrate becomes flat. The ternary phases Al8Fe2Si and Fe3Al2Si3 are identified in addition to FeAl3 and Fe2Al5. The microhardness testing recorded high values of the intermetallic layers, up to 800Hv01, which confirms the high brittleness of the intermetallic compounds.

Thermal behaviors and fluid flow controlling the geometry of 7075 aluminum alloy single tracks during liquid metal flow rapid cooling additive manufacturing

Geometry of single tracks has a significant influence on the forming efficiency, surface accuracy and internal quality of metal additive manufacturing parts. Herein, a 3D numerical model of 7075 aluminum alloy single tracks forming process during liquid metal flow rapid cooling additive manufacturing was established to reveal the effect of thermal behaviors and fluid flow on the geometry of 7075 aluminum alloy single tracks. The 7075 aluminum alloy single tracks with controllable geometries were fabricated by self-developed liquid metal flow rapid cooling additive manufacturing equipment. The results show that the variation of the solidification volume of 7075 aluminum alloy melt in spreading stage and the solidification velocity in accumulation stage results in the variety of the spreading and accumulation kinetic energy of 7075 aluminum alloy melt, which decide the geometry of 7075 aluminum alloy single tracks. The geometry of 7075 aluminum alloy single tracks can be controlled by adjusting the process parameters such as nozzle travel speed and melt temperature, which have a significant effect on the solidification volume and solidification velocity during single tracks forming process of liquid metal flow rapid cooling additive manufacturing.

Effect of electric current pulses on TiB2 particle dispersion in aluminum alloy melt

The effect of electric current pulses (ECPs) on the dispersion of TiB2 particles is investigated. The results demonstrate that Joule heating and the Peltier effect can reduce the binding force between TiB2 particles in the melt. The induced magnetic pressure, pinch force gradient and electromagnetic shock wave can disperse loose aggregations of TiB2 particles, thereby decreasing the size of the TiB2 particle clusters. The ECP parameters are found to have a large influence on the TiB2 particle cluster dispersion.

A novel electromagnetic apparatus for in-situ synchrotron X-ray imaging study of the separation of phases in metal solidification.

As a part of a research into new techniques for purifying recycled aluminium alloys, a novel electromagnetic apparatus had been developed for investigating in real-time the separation mechanisms of detrimental inclusions in aluminium alloy melts under alternating magnetic fields. The magnetic coil was designed based on the Helmholtz coil design. A viewing gap was designed for in-situ imaging studies using synchrotron X-rays. The gap was designed to maintain a uniform magnetic field in the central region where a sample is positioned. The current setup for the magnetic coil pair is able to produce a peak magnetic flux density of ~10 mT at a frequency of 25kHz. A separate electrical resistance furnace, designed to concentrically fit within the magnetic coils, was used to control the heating (up to ~850°C) and cooling of the samples. After a series of systematic tests and commissioning, the apparatus was used in a number of in-situ and ex-situ experiments.

RETRACTED ARTICLE: Metallography, Microstructure, and Wear Analysis of AA 6063/TiC Composites for Augmented Dry Sliding Property at Room Temperature

This paper summarizes the experimental investigations for augmented dry sliding property of AA 6063/TiC composite. An in situ metal matrix composite has been prepared with AA 6063 alloy for the matrix and TiC for reinforcement particulates. The fabrication of the composites is done by using potassium titanium fluoride (K2TiF6) and powder of graphite as a mixture for reaction along with molten aluminum alloy at 950 °C. The weight fraction of TiC particulates has been varied in the composites C0, C1, C2, and C3 as 0, 3, 6, and 9%, respectively. Various characterization techniques and tests were conducted to observe the morphological properties of the composites. The composites were categorized into three sets. The first set of the composites is as-cast condition. The composites were heat-treated to form two more sets, namely solutionized and solutionized-aged condition sets. The “pin-on-disk” apparatus is used for conducting the tests, wear analysis, and comparative analysis of the wear for the dry sliding condition. The study indicated a significant enhancement of the resistance to wear by composites with the higher fractions of titanium carbide (TiC) particulates and further enhancement with the heat treatment.

Gas-Enhanced Ultrahigh-Shear Mixing: An Application to Molten Aluminum Alloys

A new mixing technology that explores an integration of ultrahigh shearing with gas injection, directly into the mixer shear zone, has been applied to molten aluminum alloys. The refining and homogenizing effects were assessed through microscopic observations of solidified structures. For the set of process parameters applied, the ultrahigh shear alone caused structural refinement, which doubled the sole effect of gas flotation. Combining ultrahigh shear with gas injection magnified the structural refinement, which substantially exceeded the individual effects, caused by gas flotation and ultrahigh shearing. In addition to matrix grain-size reduction by almost two orders of magnitude, the complex intermetallic compounds, being inherently coarse in conventional castings, were also refined. The results confirmed our earlier observations made through transparent media that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultrahigh shear, leading to intensive cavitation, generated in the cylindrical rotor–stator apparatus, drastically enhanced the treatment outcome.

Improving the quality of Al-Si castings by using ceramic filters

Abstract The use of cast aluminium has still increased, so have the mechanical property requirements. By casting and also in other metallurgical processes, the inclusions enter to the molten aluminium alloy and it exhibits poor ductility or toughness. It can cause a variety of problems in the manufacture of aluminium alloy castings. Therefore, the purification of the molten aluminium alloy is one of the most important processes for improving the quality of Al-products. Filters have been used for many years in order to improve the quality of castings. The inclusions in molten secondary AlSi7Mg0.3 cast were removed using depth filtration by ceramic foam filters of 20 ppi porosity. Were used 4 types of ceramic filters in 2 thicknesses (15 and 22 mm); Brinell hardness and porosity were measured. Quality of microstructure (occurrence of oxidic particles and larger non-metallic inclusions) was observed. Experimental results show that the insertion of ceramic filters into the inlet system has contributed primarily to a decrease in porosity. On the microstructure, the inclusion of filters was not significantly reflected.

Effect of Ultrasonic Bending Vibration Introduced by the L-shaped Ultrasonic Rod on Solidification Structure and Segregation of Large 2A14 Ingots.

In order to achieve long-term and stable ultrasonic treatment in the direct chill semi-continuous casting process, a new L-shaped ceramic ultrasonic wave guide rod is designed to introduce ultrasonic bending vibration into 2A14 aluminum alloy melt. The effect of ultrasonic bending vibration on the solidification structure and composition segregation of large 2A14 aluminum alloy ingots (φ 830 mm × 6000 mm) in the process of semi-continuous casting were studied by means of a direct reading spectrometer, scanning electron microscope, metallographic microscope, and hardness test. The ultrasonic ingot treated by bending vibration was compared with the ingot without ultrasonic treatment and the ingot treated by the traditional straight-rod titanium alloy wave guide rod. The results show that, during the solidification of 2A14 aluminum alloy, ultrasonic treatment can significantly refine the grain, break up the agglomerated secondary phase, and make its distribution uniform. The macro-segregation degree of solute including the negative segregation at the edge of the ingots and the positive segregation in the center can be reduced. Through comparative analysis, the macrostructure of the ingot, treated by the L-shaped ceramic ultrasonic wave guide rod, was found to be better than that of the ingot treated by the traditional straight-rod titanium alloy wave guide rod. In particular, the grain refinement effect at the edge of the ingot was the best, the secondary phase was smaller, more solute elements can be dissolved into the α-Al matrix, and the ability of the L-shaped ultrasonic wave guide rod to restrain segregation was stronger at the edge of the ingot.

Investigation of Interfacial Phase Formation During Corrosion of Stainless Steel

Abstract: The paper shows an adaptation of thermoanalytical techniques such as Differential Scanning Calorimetry (DSC) for the investigation of interfacial phase formation during corrosion of stainless steel 316L (FeCr18Ni10Mo3)- and 16-7-3 (FeCr16Mn7Ni3)-based composites with TiO2 and ZrO2 in molten aluminium alloy (AlSi7Mg0.3). The DSC was able to detect the formation of corrosion phases on cooling after two hours of retention at 850 °C. The method allows the recognition of the solidification temperature of new corrosion phases (binary η-AlFe and ternary τ3, τ5, τ5, τ11-AlFeSi) as well as the assessment of the conversion rate of both materials. Scanning Electron Microscopy (SEM) was used for the analysis of the corrosion products.

Corrosion Behaviors of Selective Laser Melted Aluminum Alloys: A Review

Selective laser melting (SLM) is an ideal method to directly fabricate products with high geometrical complexity. With low density and good corrosion resistance, aluminum alloys are widely used as important structural materials. Microstructures and mechanical properties of SLMed aluminum alloys have been recently widely studied. Corrosion behavior as a vital concern during the service of SLMed aluminum alloy parts has also drawn many attentions. Previous studies have found that SLM-processed aluminum alloys exhibit better corrosion resistance compared to the casted and wrought counterparts for both Al-Si alloys and high strength 2xxx Al alloys, which is mainly due to the unique microstructure features of SLMed Al alloys. For Al-Si alloys, with different shapes of Si networks, the different building planes show discrepant corrosion behaviors. Owing to the rougher surface with relatively larger numbers of defects, the as-printed surface is vulnerable to corrosion than the polished. Heat treatment has a negative effect on corrosion resistance due to the breakup of Si networks. The microstructure features correlated with the corrosion behaviors were also reviewed in this paper. Some suggestions on the future study of corrosion behaviors of SLMed Al alloys were put forward.

Sustainable Optimisation of a Carousel for Foundry Processes

Foundry technology includes a family of processes that traditionally consume high amounts of energy. It is fundamental to apply the principles of Sustainable Manufacturing to increase the energy efficiency of these processes. This paper describes the research activity carried out to improve the efficiency of a carousel, which allows the automatisation of aluminium gravity die casting process, consisting of different phases: die preparation, filling with molten aluminium alloy, solidification time, die opening, and part extraction. It is demonstrated that the efficiency is a function of the disposition of the dies mounted on the carousel, due to the solidification time (which is the limiting process parameter), and different cycle times depending on the realised product. The authors propose an optimised layout, which reduces the cycle time while maintaining the same level of the casting final quality. This reduction in the cycle time significantly improves the sustainability of the foundry process.

Analysis of Microstructure and Electric Conductivity in Al-RE Alloy by Heat-Treatment Condition.

In this study, we investigate the microstructure and mechanical properties of as-extruded Al-1.0RE alloys. The molten Aluminum alloy was maintained at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod measuring 12 mm thick with a reduction ratio of 38:1. The microstructure and electric conductivity properties of as-extruded Al-1.0RE alloy under different annealing processes were investigated and compared. After extrusion, the intermetallic compound having a needle shape in the cast state was finely decomposed based on the direction of extrusion. Significant changes in the microstructure were detected after annealing at 500 °C with fragmentation and sphering of eutectic particles. The annealing temperature of Al-1.0RE alloy increased proportionally to the electrical conductivity. The formation of Al-RE intermetallic compounds increases the electrical conductivity and improves the mechanical properties of the alloy through precipitation hardening.

Corrosion characterization of Al 6061 / Red Mud MMCs in hydrochloric Acid

Abstract Composites materials are in demand now a day due to their decreased weight and improved properties with respect to mechanical behaviour. They also exhibit increased corrosion resistance in acid, salt and alkali mediums. In this paper experiments related to the corrosion properties of composites made up of Aluminium 6061 reinforced with red mud particulates. Both matrix and reinforcement are available commercially. Matrix Alluminium 6061 alloy is an important alloy used in many applications. When aluminium is removed from bauxite ore the waste obtained is red mud.. It is found to contain the oxides of iron, silicon, aluminium, zirconium, titanium and vanadium. Composites are manufactured by creating a vortex in the molten aluminium alloy. Vortex is created by introducing an impeller after heating matrix to its melting point. Red mud particulates without any coating are subjected to preheating and poured to the vortex, entrapped gas bubbles are removed by adding hexa chloro ethane tablets. Then after stirring the mixture is poured in to cast iron moulds which are pre heated. Composites containing three different weight percentage of red mud reinforcement. For comparison matrix alloy was also casted. Cylindrical specimen and rectangular specimen were machined form all the composites and matrix alloy according to ASTM standards. The composites were characterized with respect to weight loss and polarization test in hydrochloric acid. Both the tests were conducted according to ASTM standards. Electro chemical work station was used to conduct the potentiodynamic polarization test. Corrosion resistance of composites were found to be increased in the tests more than the matrix alloy. Therefore composites are preferred instead of matrix alloy in all the applications

Effect of pouring temperature on cast Al/SiCp and Al/TiB2 metal matrix composites

AbstractThe effect of pouring temperatures of an ex situ (Al/SiCp) and in situ (Al/TiB2) metal matrix composites (MMCs) synthesized using stir casting method were studied. The Al/SiCp composite were fabricated by mixing of 6wt.% of SiCp into cast A356 aluminium alloy melt and poured at diverse pouring temperatures (730∘C, 750∘C and 770∘C). The Al/TiB2 MMCs were obtained by melting A356 aluminium alloy and mixing of KBF4 and K2TiF6 precursor salts whose stoichiometric ratio composition corresponds to 6wt.% of TiB2 reinforcement and other parameters were constant (stirring speed 300 RPM and holding time 30 minutes). The composite melt was poured into the permanent mould with varied pouring temperatures (800∘C, 820∘C and 840∘C). Coarser and homogenous SiC particles were presented in the Al/SiCp MMCs, whereas, finer and uniformly distributed TiB2 particles were appeared at the MMCs of Al/TiB2. The mechanical properties viz. tensile strength, fracture toughness and hardness of Al/SiCp and Al/TiB2 MMCs were experimentally determined as per the ASTM standards and compared. Higher tensile and fracture strength were occurred at the MMCs of Al/TiB2 as compared to Al/SiCp MMCs and base alloy of aluminium as well. Maximum hardness was attained at the pouring temperatures of 820∘C and 750∘C in the MMCs of Al/ TiB2 and Al/SiCp, respectively.

Design of a Test Rig for the Characterization of Thermal Fatigue and Soldering Resistance of the Surfaces of Tool Steels for High‐Pressure Die‐Casting Dies

The conceptualization and development of a test rig able to reproduce thermal stresses and contact with molten aluminum alloy, typical of high‐pressure die‐casting dies, are described. During the test, a hot‐work tool steel sample is cyclically heated by contact with molten aluminum alloy (AlSi11Cu2(Fe)) and then cooled by the spraying of a water‐diluted silicone‐based lubricant. A finite element method (FEM) simulation is setup to determine the temperature at different depths beneath the sample surface during thermal cycling and is experimentally validated to design the proper sample geometry aimed at reproducing the stress/strain conditions experienced by a die‐casting die insert. A tensile–compressive stress state is achievable on the surface of the sample by machining a notch with a suitable radius, which is able to produce a plastic strain comparable with the insert one. A thermally induced stress–strain fatigue loop is determined for both the sample and the component. Temperatures are monitored discontinuously by infrared (IR) thermography after heating and continuously by thermocouples placed at a reference depth of 5.5 mm. Finally, the optimized testing conditions are validated experimentally: both thermal cracking and soldering phenomena are successfully reproduced on a lab‐scale test rig.

The corrosion of aluminum matrix composite <i>in situ</i> based on Al–7Si–1Fe alloy

The results of a comparative research into the corrosion resistance of an aluminum matrix composite material produced by the oxygen lancing of a prehydrogenated aluminum alloy melt based on Al–Si–Fe with an iron content of over 1.0% and Al–7% Si alloy with an iron content of up to 0.3% modified by ligature 5Al–Ti for 2% are shown. The aluminum-alloy corrosion was conditioned by the film discontinuity of the oxide on some phases, primarily Al5SiFe. The composite and reference alloy-sample couples with a diameter of 15 mm and a length of 50 mm were put to the test in a 7% solution of NaCl salt fog in SFC-1 chamber on suspension brackets at a temperature of 22°C for 300 h. The results show the mass loss close values of the samples, despite the significantly higher iron content in the composite, because particles 100–200 nm in size formed in the melt by lancing are deposited on the composite phase boundaries, reducing the interaction surface area with the corrosive environment. The researched composite material can be recommended as a corrosion-resistant alternative to alloys with elevated iron content, which are used for high pressure die casting (HPDC).

Effect of Electric Fields on the Structure of an Aluminum Alloy during Magnetohydrodynamic Treatment

The microstructure of a 1417M alloy after magnetohydrodynamic (MHD) treatment has been studied. An electric field induced in the aluminum alloy melt is shown to cause electric transfer and to homogenize its structure. During the formation of an ingot upon MHD treatment, intermetallic phase dendrites are preferably oriented along the lines of the induced electric field.

Application of Cold Metal Transfer Welding for High Pressure Die Casting Mold Restoration

This paper presents results of the research focused on the possibility of the restoration of the shape parts of molds made of X15CrNiSi20-12 (EN 100 95) heat-resistant austenitic chromium-nickel stainless steel working in high-pressure die casting of aluminum alloys by clad welding. There were tested two welding wires—E Ni 6625 and E 18 8 Mn B 2 2—deposited on X15CrNiSi20-12 (EN 100 95) tool steel using cold metal transfer (CMT) welding in a protective atmosphere of Ar. The resistance of welds was tested against dissolution in molten aluminum alloy ENAC-AlSi9 and the testing procedure was designed. The resistance of welds against dissolution were assessed by exposition of welded clads in an aluminum melt for 120 and 300 min. The EDX semi-quantitative microanalyses of element distribution were performed at the welding–melt interface, and build-ups were also observed on the surface of welded clads.

Corrosion behavior of hybrid coconut shell powder and silica carbide reinforced aluminium composite towards aggressive biofilm attack

This study enveloped innovative uses of a hybrid agro waste and silica carbide incorporated with aluminium as a new hybrid composite materials for marine application. In this study, the purpose of adding coconut shell powder (CSP) from the agro waste and silicon carbide (SiC) as reinforcement aluminium composites materials for combating corrosion problem. The CSP was incorporated into the molten aluminium alloys varies from 0%, 5%, 10%, 15% and 20% of weight percentages. The corrosion behaviour was determined by weight gain measurement (WGM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). As a results, 5% CSP reinforcement in hybrid aluminum composites contribute to excellent corrosion resistance performance by shifting the polarization curve towards the positive region, increases the value of polarization resistance, Rp and reduces the Icorr value. It can be concluded that, by adding CSP into aluminium composite has significantly increase the corrosion resistance towards a severe biofilm attack.

Preparation and properties of melted zircon

The data on the melting of zircon with the addition of glassforming oxides are given. The structure of the synthesized materials is represented by baddeleite and glass phase, which determine the operational characteristics of the refractory. Corrosion tests of samples of melted zircon in molten aluminum alloys showed their zero wettability and minimal corrosion. The material with an less than 2 % SiO2 was obtained when melted zircon was treated with a solution of 10 % HF. The threefold decrease in the silica content in the melting product was observed in electric arc furnace with carbothermic melting of zircon.