Cast Aluminum Alloy A356 Research Articles

Influence of Y Content and T6 Heat Treatment on the Organization and Mechanical Properties of Cast A356 Aluminum Alloy

The effect of Y content on the microstructure of A356 aluminum alloy and the mechanical properties of the alloy under T6 heat treatment was investigated. The results show that with the addition of 0.3 wt.% rare earth Y, the grain size of the cast A356 aluminum alloy reaches a minimum and the mechanical properties reach an optimum. After the T6 heat treatment, the grain structure of the alloy was further reduced and the mechanical properties were further improved. Compared to the cast A356 aluminum alloy without Y, the average α-Al grain size is reduced by 53.4%, the secondary dendrite SDAS by 32.2% and the average length of eutectic Si particles by 82.0%. The ultimate tensile strength (UTS) and elongation (El) increased to 280.75 MPa and 14.43% respectively, and the Vickers hardness increased to 102.9 HV.

The Effect of Fe Content on the Microstructure and Tensile Properties of Friction-Stir-Welded Joints in Recycled Cast Aluminum Alloy.

The presence of the impurity element Fe significantly influences the overall performance of recycled aluminum alloy. This study aims to elucidate the impact of Fe content on the microstructure and tensile properties of friction-stir-welded (FSW) joints in recycled cast A356 aluminum alloy. Three samples with varying Fe content were prepared for FSW joints. The quality of the weld zone was meticulously assessed through macrostructure and microstructure analyses. The tensile strengths of the joints were carefully evaluated and correlated with the microhardness and microstructure of the weld zone. The research findings reveal that, among the three fabricated joints, the one with an Fe content of 0.3 wt.% demonstrates the most favorable tensile performance. This particular joint exhibits the highest tensile strength of 153 MPa, commendable yield strength of 90 MPa, and a favorable elongation of 5.7%. The mechanisms responsible for grain refinement in the weld nugget zone involve plastic deformation and dynamic recrystallization. Significantly, the disruptive effects of friction-stir action on eutectic silicon phases and rich iron phases emerge as crucial factors contributing to the enhanced performance of the weld nugget zone in the welded joint.

Microstructural Evolutions and Strengthening Mechanism according to the Aging Temperatures of a High Si Cast Aluminum Alloy

A356 cast aluminum alloy contains 7 at.% Si and 0.3 at.% Mg, producing an approximately 50% eutectic microstructure. This high Si content and various casting conditions play a significant role in strengthening A356 alloy, by controlling the eutectic morphology and precipitates of other intermetallic compounds. Understanding how Si-related precipitates and clusters are soluble in the α-matrix is necessary to provide high strength and fatigue resistance to A356 alloys. The aging heat-treatment temperature in the A356 alloy most likely promotes the formation of these precipitates and clusters. The A356 samples were differently aged at temperatures of 110 oC and 130 oC for 2 h, and were labeled 110A, and 130A, respectively. 110A was found to have improved mechanical properties, such as high strength and elongation, compared to 130A, which may be attributed to the formation of secondary phases in the α-phase matrix. Scanning and transmission electron microscopy and atom probe tomography analyses demonstrated Ti2Si precipitation and various-sized cluster formations in 110A. In contrast, 130A had fewer clusters than 110A. Therefore, different aging heat-treatment temperatures relate to a change in the behavior of atoms, affecting the mechanical properties.

Recycling of titanium as reinforcement in cast aluminium alloy A356 for improving the microstructural refinement and mechanical performance towards a sustainable material development

A356 is one of the most commonly used Al-Si cast alloy containing copper, magnesium and titanium, as other predominant alloying elements. Due to its wide application in domains where dominant loading is compressive in nature, various research work is being carried out to improve the compressive performance of A356 alloy by adding particulate reinforcement in it, converting it to metal matrix composite. However, ceramic particles added as reinforcement have always been posing challenges due to the poor wettability and weak interface bonding. In the present research work, an attempt is made to recycle titanium in a greener way of adding it to Aluminium alloy as a strengthening reinforcement which shall address the interface boding issues due to better compatibility of Titanium and Aluminum – both being metals. 5% by weight of micro and nano-sized Titanium particles is added to A356 through stir casting method. Cast material was then subjected to hot extrusion. The as-cast and extruded composites are studied for the micro structural evolution and mechanical performance against the base alloy. Results indicate that the performance of the composite is found to be significantly enhanced as compared with the base alloy in terms of strength, hardness and ductility. Increased mechanical performance is attributed to refinement of dendrite size, presence of uniformly distributed Ti particle, and partial diffusion of Ti into the Al matrix.

The effect of pre-drilling on the characteristics of friction drilled A356 cast aluminum alloy

The friction drilling process utilizes frictional heat to increase the thickness of sheet metal parts by making holes with bushes using a non-traditional drilling tool. Unfortunately, cracks are found in the formed bushings during friction drilling of brittle materials. The purpose of the present study is to improve the quality of friction-induced bushes in brittle A356 aluminum sheets via a performance of a pre-drilling with different diameters (2, 2.5, and 3 mm). The pre-drilling is aimed to reduce cracks and petal formation as compared with the solid sheets. The friction drilling processes were carried out by a K100 conical tool, with 10 mm diameter and 58° cone angle. The friction drilling parameters involve different rotational speeds (2000, 3000, and 4000 rpm) as well as different feed rates (40, 60, and 80 mm/min). The characteristics of the thermally induced bushes (shape, dimensions, and surface roughness) were investigated in solid and pre-drilled sheets. Furthermore, we studied the microstructure evolution and hardness distribution in the thermo-mechanical affected zone and the heat-affected zone surrounding the bush. It was found that, the formed bushings in the pre-drilled sheets did not have cracks or petal formation in comparison with the other formed bushes in the solid sheets. The pre-drilled specimens showed an average bushing height increase from 5 to 6 ± 0.8 mm with the increase of the tool rotational speed from 2000 to 4000 rpm. At rotational speeds of 2000 and 4000 rpm, the pre-drilled specimens with a diameter of 2.5 mm had a bushing height which is 0.5 ± 0.2 mm greater than the other pre-drilled specimens. In addition, the surface roughness of the pre-drilled sheets decreased with the increase of the rotational speed and/or reduction of the feed rate. Moreover, the microstructure near the drilling zone exhibited a fine Si particles distribution. However, the hardness values near the drilled surfaces were 15 ± 8 HV lower than those of the base metal in both solid and pre-drilled sheets.

Three-Point Bending Properties of Hybrid Multi-Materials Using Adhesive Bonding Dependent on Strength Difference between Steel and Aluminum.

The mechanical behaviors of two multi-materials, DP590 (steel sheet)–A356 (cast aluminum alloy) and SS330 (steel sheet)–A5052 (aluminum sheet), were studied. A structural adhesive was used for the joining of steel and aluminum at adhesion strengths of 10, 22, and 30 MPa. To demonstrate that the three-point bending properties depend on the difference in strength between steel and aluminum and adhesion strength, optical microscopy (OM), scanning electron microscopy (SEM), and finite-element analysis (FEA) were performed. According to the results of the bending tests on both multi-materials under the same stacking conditions, the flexural stress increased with the improvement in the adhesion strength until interface separation or aluminum fracture. At the same adhesion strength, the DP590 (lower)–A356 (upper) and SS330 (upper)–A5052 (lower) configurations exhibited a tendency to decrease in the sudden stress drop due to aluminum fracture and interface separation. The bending results were analyzed through the FEA and the stress distribution as a function of the stacking and adhesion strength was confirmed.

Effect of NaOH on plasma electrolytic oxidation of A356 aluminium alloy in moderately concentrated aluminate electrolyte

Plasma electrolytic oxidation(PEO) of cast A356 aluminum alloy was carried out in 32 g/L NaAlO2 with the addition of different concentrations of NaOH. The stability of the aluminate solution is greatly enhanced by increasing the concentration of NaOH. However, corresponding changes in the PEO behaviour occur due to the increment of NaOH concentration. Thicker precursor coatings are required for the PEO treatment in a more concentrated NaOH electrolyte. The results show that the optimal NaOH concentration is 5 g/L, which improves the stability of storage electrolyte to about 35 days, and leads to dense coatings with high wear performance (wear rate: 4.1×10−7 mm3·N−1·m−1).

Parametric investigations in pulsed laser-assisted hatch patterning and nitriding of A356 cast aluminum alloy in liquid nitrogen environment for improving mechanical and tribological properties

In the present study, a novel technique to replace conventional honing with a laser hatch patterning accompanied by nitriding called pulsed laser hatch patterning and nitriding (PLHN) process has been identified and reported in detail. Effect of process parameters like laser wavelength (532 and 1064 nm) and N2 gas flow rate (5–35 L/min) on the nitride layer quality, average roughness, hardness, and elevated temperature tribological performance of A356 cast Al alloy has been investigated. The formation of a thin AlN layer was confirmed from (GIXRD and XPS) analysis. The crack-free nitride layer was produced with a maximum thickness of 13.48 ± 0.53 µm, and 11.35 ± 0.34 µm using laser wavelengths 532 nm (at 15 L/min) and 1064 nm (at 25 L/min), respectively. At these optimized process parameters, the PLHN specimen processed at 532 and 1064 nm laser wavelengths showed a maximum of 212.57 and 144.73% increment hardness values as compared to the base material (1.52 Gpa). While the wear rate (200 °C) was reduced by 43.25% and 36.48% for the PLHN specimen processed at 532 nm and 1064 nm, respectively in comparison with the base material.

Experimental Investigation on Tensile Properties and Yield Strength Modeling of T5 Heat-Treated Counter Pressure Cast A356 Aluminum Alloys

In the present study, experimental investigations on microstructures and tensile properties of an counter-pressure cast (CPC) A356 aluminum alloy under different T5 heat treatment conditions were conducted in the temperature range of 160–200 ∘C for 1–48 h. As the T5 heat treatment time increased, both tensile and yield strength of the CPC A356 alloy either continuously increased at 160 ∘C until 48 h of heat treatment time or increased until the maximum strength values were achieved and then decreased, showing peak aging behavior at 180 and 200 ∘C. Changes in microstructural aspects, such as size and aspect ratio, of the eutectic Si, Mg and Si distribution in the α-Al grain and the stability of intermetallic compounds were found to be negligible during the T5 heat treatments employed in the present study. From high resolution-transmission electron microscope (HR-TEM) analysis, nanosized needle-like β″ precipitates were identified in the specimens, showing a significant increase in strength after the T5 heat treatment. Based on the measured tensile properties and observed microstructure changes, a yield strength model was proposed to predict yield strengths of CPC A356 alloys at arbitrary T5 heat treatment conditions. The calculation results of the model showed good agreement with the experimental data obtained in the present study. From the model calculations, the optimal T5 heat treatment time or temperature conditions were suggested.

Achieving high-strength metallurgical bonding between A356 aluminum and copper through compound casting

Due to stable surface oxides on the solid copper surface and the ease of forming Al 2 O 3 films at the aluminum melt surface, it is difficult to achieve high-strength metallurgical bonding between the two materials through compound casting. In this research, a novel surface coating method for the copper inserts, namely hot-dip Sn-coating, has been applied. Through this method, a high-quality bond between a cast aluminum alloy A356 and commercially pure copper was achieved through a gravity compound casting process. Tensile tests showed that a maximum ultimate tensile strength (UTS) of 90.8 MPa could be obtained for the bimetal interface. Microstructures formed in the aluminum/copper interface were studied by optical- and scanning electron microscopy, while a sessile drop wetting test was used to study the wettability between the aluminum melt and Sn-coated copper substrates. The effects of Sn-coating on the wettability and the formation of interfacial microstructure were discussed. • Continuous metallurgical bond was achieved in aluminum/copper compound castings. • Sn-coating of copper significantly improved wetting between aluminum and copper. • Ultimate tensile strength of 90.8 MPa was measured for the Al/Cu castings. • Effect of the Sn coating layer was discussed.

INVESTIGATION OF DISTINCTIVE SOLUTIONIZING PROCESS PARAMETERS ON SIGNIFICANTLY INCREASING IN STRENGTH AND DUCTILITY OF As-CAST AZ80 Mg ALLOY

A distinctive solutionizing process parameter was developed and performed to significantly enhance strength and ductility of aged AZ80 Mg alloy. The microstructure-processing-properties relationship was studied to help elucidate the mechanism. Microstructure and mechanical properties were studied by using optical microscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction, hardness and tensile testing. The results show that the solutionization at 380°C/10h followed by 420°C/10h promoted significant dissolution of eutectic Mg17Al12 and intermetallic phases. After standard aging at 200°C/10h, the formation of high-density precipitates Mg17Al12 with more spheroidization precipitates and lesser discontinuous precipitates morphology, which was not observed in conventional heat treatment for aged AZ80 Mg alloy. Fine precipitates Mg17Al12 resulted in a significant increase in ultimate tensile strength (50.3%), yield strength (35%), elongation (106%) and hardness (40%) compared to conventional heat treated cast AZ80 Mg alloy. These properties are comparable to the commonly used aerospace grade cast aluminium alloy A356.

Effects of process parameters on structure and corrosion behavior of PEO coated A356 alloy

Plasma electrolytic oxidation (PEO) coatings were formed on cast A356 aluminum alloy by applying various process parameters (current density, duty cycle and processing time) in silicate based electrolyte. The phase composition of coatings was analyzed by x-ray diffraction (XRD), surface and cross section morphology and microstructure of coatings were characterized by scanning electron microscope (SEM). The Results of x-ray diffraction showed that all coatings are composed of gamma alumina. Coating produced in higher current density, duty cycle and time was more compact with fewer amounts of defects. Thickness and roughness of coatings surfaces were measured by Eddy current gauge and surface roughness tester, respectively. The thickness of the Coatings was in the range of 3–7 μm and it increased by increasing current density and time, but duty cycle did not have a noticeable effect on it. Corrosion resistance of bare and coated samples was evaluated by polarization test in 3.5 wt% NaCl solution. Sample S176 showed the best corrosion resistance with corrosion current density of 4.17 × 10−8 A.cm−2 and polarization resistance of 6.31 × 105 Ω.cm2 that attributed to its more dense structure.

Mechanical properties of steel-aluminum multi-materials using a structural adhesive

In this study, a DP590 steel sheet and A356 cast aluminum alloy were joined using a structural adhesive to evaluate the effect of the mechanical behavior depending on the adhesion strength. The tensile test results of the steel-aluminum multi-materials showed that the elongation of aluminum prior to fracture tends to increase with increasing adhesion strength. SEM observations of the tensile specimen fracture surface in A356 single material showed cracks that propagated along the interface of the eutectic Si phase and Al phase. On the other hand, the multi-materials tended to produce considerable deformation inside the primary Al due to the uniform dispersion of stress throughout the joint surface. Bending under the same stacking sequence conditions of multi-materials, the flexure stress increases until interfacial separation because of the uniform deformation of different materials as the adhesion strength increases. In addition, the results of bending on the steel (upper) - aluminum (lower) condition showed interfacial separation and aluminum. This was attributed to aluminum with weak ductility under a tensile load, which resulted in fracture. On the other hand, in the case of the aluminum (upper) - steel (lower) condition, the multi-materials act like a single material, so that the aluminum did not break until the end of the test.

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.

Evaluation of the reheating behavior of the cooling slope cast A356 and A380 aluminum alloys

A356 and A380 alloys are two well-known hypoeutectic Al-Si casting alloys in the non-ferrous casting industry and drew significant attention for semi-solid applications. The cooling slope casting method for producing materials with non-dendritic microstructure is one of the simplest liquid route techniques. In the beginning, microstructural differences of both alloys produced with 30° and 60° tilt angles were examined. It was observed that the angle change has a limited effect on A380 and it is almost non-effective for A356 as-cast structures. The samples were then subjected to the reheating processes for different times and the effects were investigated by measuring the average shape factor and the grain size values. In addition to the natural grain growth, it is understood that the changes in the eutectic are also effective on the properties. The rapid solidification of the melted eutectic by quenching the reheated samples modified the eutectic structure and improved the hardness. On the other hand, grain growth reduces hardness naturally. Additionally, it was observed that the increase in sphericity was supported by the liquid phase formation and it was determined that A356 alloy was more sensitive to reheating and formed larger grains than A380 alloy for the same reheating periods.

Tribological behavior of A356−CNT nanocomposites fabricated by various casting techniques

Abstract Tribological behaviors of monolithic A356 aluminum alloy castings and A356−CNT nanocomposite castings, fabricated by fully liquid and semisolid routes were examined. Samples were prepared by melt agitation, rheocasting, stir casting, and compocasting techniques. Effects of addition of carbon nanotubes (CNTs), casting process and the applied load on wear properties and mechanisms were investigated. It was found that wear loss, wear rate and friction coefficient of nanocomposite samples remarkably declined by the addition of CNTs. Moreover, changing the casting process from fully liquid to semisolid routes, plus increasing fractions of the primary phase were the two factors that improved the wear properties of the investigated samples, especially nanocomposite ones. In addition, it was revealed that adhesion and delamination were the dominant wear mechanism of the monolithic samples produced by fully liquid and semisolid routes, respectively. However, regardless of fabrication techniques, the abrasion was the main wear mechanism of nanocomposite samples.

Development of A356/Al2O3 + SiO2 surface hybrid nanocomposite by friction stir processing

Surface hybrid nanocomposite layers reinforced with nano-sized Al2O3 and SiO2 powders on the A356 cast aluminum alloy matrix were developed by friction stir processing (FSP). The optical and scanning electron microscopy (SEM) were used to study the microstructure of samples, as well as to investigate the size and morphology of the reinforcement powders. Microhardness and nanoindentation tests were applied to characterize the mechanical properties of the samples. To examine corrosion behavior of the samples, the potentiodynamic polarization and electrochemical impedance spectroscopy were used. In addition, the corroded surfaces were investigated by SEM. FSP of the alloy leads to the fragmentation of coarse silicon needle-shaped particles and coarse dendrites of primary aluminum, reduction in porosity and uniform distribution of fine silicon particle with average size about 3 μm in the aluminum substrate. Furthermore, the microstructural analysis showed a uniform distribution of reinforcement particles inside the nugget zone. The surface hybrid nanocomposite resulted in enhanced mechanical and corrosion properties compared with A356 Al alloy and the FSPed A356.

Nanoceria induced grain refinement in electroless Ni-B-CeO2 composite coating for enhanced wear and corrosion resistance of Aluminium alloy

Nickel-based coatings on aluminium with specific surface properties are of great interest for anti-corrosive, anti-wearing, and self-lubricating applications. In the present study electroless Ni-B alloy and Ni-B-CeO2 nanocomposite coatings were formed on 356 aluminium alloy surfaces. Ceria incorporation to Ni-B coating reduces the average nodular grain size from 1150 nm to 650 nm and Ni crystallite size from 15 nm to 9.97 nm. Ni-B-CeO2 nanocomposite shows remarkable improvement in microhardness of 684 VHN compared to pure Ni-B coating with 424 VHN. Enhanced wear resistance and reduction in friction coefficient are observed for the nanocomposite coatings compared to 356 Al alloy and Ni-B alloy coating. Potentiodynamic polarization measurements show a remarkable reduction in the corrosion current density for ceria added nanocomposite coating (2.48 × 10−6 A cm−2) than that of the particle-free counterpart (11.18 × 10−6 A cm−2). Uniform Ni-B-CeO2 composite coating was obtained on centrifugally cast A356 aluminium alloy cylinder liners which have potential applications in automotive systems.

Multiaxial fatigue life estimation of defective aluminum alloy considering the microstructural heterogeneities effect

The Al–Si–Mg high-cycle fatigue behavior is mainly affected by the microstructural heterogeneities and the presence of casting defects. This attempt aims to develop an analytical approach based on the evaluation of the highly stressed volume caused by local porosities and defined as the affected area methodology. The proposed approach is able to predict the aluminum alloy fatigue response by considering the effect of microstructure described by the secondary dendrite arm spacing and its correlation with the defect size effect. A representative elementary volume model is implemented to evaluate the stress distribution in the vicinity of the defect and to determine its impact on the high-cycle fatigue resistance. Work hardening due to cyclic loading is considered by applying the Lemaitre–Chaboche model. The Kitagawa–Takahashi diagrams corresponding to different microstructures and for two loading ratios: R σ = 0 and R σ = −1 were simulated based on the AA method. Simulations were compared to the experimental results carried out on cast aluminium alloy A356 with T6 post heat-treatment. The results show clearly that the proposed approach provides a good estimation of the A356-T6 fatigue limit and exhibits good ability in simulating the Kitagawa–Takahashi diagrams for fine and coarse microstructures.

Quantification of Entrainment Damage in A356 Aluminum Alloy Castings

Aluminum melts sustain damage to its quality when surface oxides are entrained into bulk liquid. To quantify the extent of entrainment damage, four castings were produced in reduced pressure test (RPT) apparatus; one machined out of the continuously cast ingot, and the other three by pouring the metal from a height of 25, 37.5, and 150 mm. Analyses of RPT samples via micro-computer tomography (μ-CT) scanning demonstrated that the number and volume fraction of pores in aluminum casting increased with increasing velocity of the liquid. However, average and maximum pore sizes first increased with velocity, then decreased, indicating that additional kinetic energy of the metal breaks entrained bifilms. The investigation of the cross sections of RPT specimens via scanning electron microscopy and X-ray maps showed that oxygen was present inside, around, and between the pores, providing further evidence that bifilms act as initiation sites for pores. Moreover, there were unopened bifilms near pores, suggesting that entrainment damage is more extensive than what can be ascertained by the pore size measurements.