Mechanical Properties Of A356 Alloy Research Articles

Microstructure and mechanical properties of A356 alloy with yttrium addition processed by hot extrusion

The effects of the rare earth element yttrium (Y) and hot extrusion on the microstructure and mechanical properties of A356 alloy were investigated by mechanical properties testing and microstructure observation. The results indicate that the addition of Y improves the microstructure of the as-cast alloy. The distribution of primary α-Al is uniform and orderly. The long needle-like eutectic Si phases and β-Fe phases turn to strips and short rods. When the content of Y increases to 0.2 wt%, the mean diameter of α-Al (40.3 μm) and the aspect ratio of the eutectic Si phase (2.3) reach the minimum values, which are 68.9% and 86.1% lower, respectively, than that of the alloy without Y addition. Under extrusion stress, the shape of the eutectic Si phase is changed from long rod-like to near grain-like after solution treatment. The size of the eutectic Si phase is significantly reduced. The needle-like β-Fe phases are squeezed and broken. The mechanical properties of the as-extruded alloy are significantly improved compared to the as-cast alloy. When the rare earth content is 0.2 wt%, the ultimate tensile strength, hardness and elongation of the alloy reach the maximum values, which are 328.2 MPa, 110.4 HV and 21.3%, respectively, and increase by 42.01%, 37.71% and 481.91%, respectively, in comparison to the as-cast alloy without Y addition.

Influence of Rare Earth Additions on the Microstructure and Mechanical Properties of Al7Si0.3Mg Alloys Processed by Semi-Solid Die Casting and Gravity Die Casting

Microstructures with fine globular grains and refined eutectic structures are important to enhance the mechanical properties of A356 alloys processed by semi-solid and gravity die casting. Rare earth (RE) additions have been shown to be capable of refining both the α-Al particles as well as modify the eutectic phase of alloys. In semi-solid die casting, Al7Si0.3Mg alloys with RE concentrations (0, 0.1 and 0.4 wt.%) were used to prepare semi-solid slurries using the SEED (Swirling Enthalpy Equilibrium Device) method, and subsequently semi-solid die cast. The same compositions of alloys were also applied to gravity die casting. The microstructure and mechanical properties of castings in two processes have been characterized. Compared to the grains produced in gravity die casting, globular grains with small size (260 μm) in the semi-solid die casting significantly enhance the UTS and elongation of alloys. Although the size of grains had no change with increasing RE concentrations in alloys. The Al-Si eutectics were changed to refined morphology with the 0.1 wt.% RE addition, which enhanced the ductility of alloys in two processes. When increasing the RE addition to 0.4 wt.%, the RE-rich phases precipitated at grain boundaries, which decreased the UTS and elongation of alloys.

Room Temperature Mechanical Properties of A356 Alloy with Ni Additions from 0.5 Wt to 2 Wt %

In recent years, the influence of Ni on high-temperature mechanical properties of casting Al alloys has been extensively examined in the literature. In the present study, room temperature mechanical properties of an A356 alloy with Ni additions from 0.5 to 2 wt % were investigated. The role of Ni-based compounds and eutectic Si particles in reinforcing the Al matrix was studied with image analysis and was then related to tensile properties and microhardness. In the as-cast condition, the formation of the 3D network is not sufficient to determine an increase of mechanical properties of the alloys since fracture propagates by cleavage through eutectic Si particles and Ni aluminides or by the debonding of brittle phases from the aluminum matrix. After T6 heat treatment the increasing amount of Ni aluminides, due to further addition of Ni to the alloy, together with their brittle behavior, leads to a decrease of yield strength, ultimate tensile strength, and Vickers microhardness. Despite the fact that Ni addition up to 2 wt % hinders spheroidization of eutectic Si particles during T6 heat treatment, it also promotes the formation of a higher number of brittle Ni-based compounds that easily promote fracture propagation.

Effects of Al-Ti-B-Sr Master Alloy on the Microstructure and Mechanical Properties of A356 Alloy

A356 alloy was refined with a new master alloy of Al-5Ti-B-10Sr. The microstructure and mechanical properties of the refined A356 alloy with different content of master alloy (0, 0.1, 0.3, 0.5 and 0.7 wt.%) were investigated. The results show that the refining effect becomes stronger as the master alloy content increasing from 0.1 to 0.3 wt.%, and then shows slight decrement until 0.7 wt.%. An optimal combination of the tensile strength (193 MPa) and the elongation (17.8%) of as-cast A356 alloy was achieved with 0.3 wt.% of refining master alloy. Compared to the non-modified A356 alloy, the tensile strength and the elongation were improved by 10% and 242%, respectively.

Investigation on the Mechanical Properties of A356 Alloy Reinforced AlTiB/SiCp Composite by Semi-Solid Stir Casting Method

Employing the semi-solid stir casting method to strengthen MMCs by SiCp particle was the simplest way in the casting process. The strength and toughness of a composite material can be obtained through a combination of the A356 / Al7Si composites and SiCp particle. The purpose of this study was to investigate the difference in the mechanical properties of Al7Si1Mg/SiCp and Al7Si1Mg1.5TiB/SiCp composites, as well as the changing effects on the extra level of SiCp particle. Al7Si was used as matrix strengthened by SiCp with the percentage variations of 10, 15, 20 wt%. The additional level of 1.5 wt% AlTiB aimed for increasing the matrix grain refinement. The semi-solid stir casting method was performed to spread the SiCp particles evenly in the liquid matrix. The results of the study were the tensile strength value of as much as 143 MPa or the increase of 22.16%. The biggest yield strength on the Al7Si1Mg1.5TiB/SiCp composite was averagely as much as 106 MPa. The highest impact toughness was averagely amounted to 4.74 J/mm2. The lowest porosity value was averagely 2.10%. The morphology of the composite between the reinforcing particle and the matrix was able to unite and to be dispersed evenly. The present study was conducted through density test, tensile test, impact test, microstructure test, and SEM.

Improvement of mechanical properties of Al-Si alloy with effective grain refinement by in-situ integrated Al2.2Ti1B-Mg refiner

Abstract In order to improve the effectiveness and stability AlTiB grain refiners for cast Al-Si alloys, the present study investigated the grain refinement of cast Al-Si alloys using an in-situ integrated Al2.2Ti1B-Mg master alloy, which was synthesized through two-step chemical reaction to create TiB2 particles and magnesium aluminate (MgAl2O4) phase in the master alloy. Experimental results showed that the fine equiaxed grains were obtained for A356 alloy treated with Al2.2Ti1B-Mg master alloy. In comparison with the α-Al grain size at a level of 950 ± 135 μm and 620 ± 95 μm for A356 alloy without refinement and refined by conventional Al5Ti1B master alloy, the fine grain size of about 320 ± 50 μm could be obtained for A356 alloy refined by Al2.2Ti1B-Mg master alloy. The yield strength, ultimate tensile strength and elongation of the A356 alloy refined by Al2.2Ti1B-Mg was 257±5 MPa, 313±5 MPa and 7.8 ± 0.5% respectively, which was increased by 6% (14 MPa), 3% (8 MPa), and 13% (1.0%) in comparison with that obtained by Al5Ti1B. The improvement of mechanical properties of A356 alloy after treated by Al2.2Ti1B-Mg was attributed to the effective nucleation of α-Al phases. The formation of MgAl2O4 layer on the TiB2 surface was expected to reduce the misfits between TiB2 and Al and promote the nucleation of α-Al, and therefore improve the effectiveness of grain refinement.

Effect of heat treatment on microstructures and mechanical properties of A356 alloy cast through rapid slurry formation (RSF) process

The effect of T5 heat treatment on microstructure and mechanical properties of A356 alloy was observed. The as-cast A356 alloy exhibited coarse dendrites and long Si needles. RSF process changed the dendritic α-Al phase to globular morphology which helps in improving the mechanical properties of the alloy. The addition of 0.6wt-% Al–5Ti–1B grain refiner refined the average grain size of primary α-Al phase. T5 heat treatment at 170 °C for 20 h in different processing conditions was given to A356 alloy. T5 heat treatment led to further refinement of α-Al phase and Si needles, precipitation hardening due to Mg2Si phase and reduction in the porosity level (%). The Quality Index for A356 alloy in different processing conditions was also measured. Results showed that RSF process with the use of baffles, addition of grain refiner and T5 heat treatment had improved the mechanical properties over other processing conditions.

Processing and Microstructure Characteristics of As-Cast A356 Alloys Manufactured via Ultrasonic Cavitation during Solidification

AbstractRecent studies have showed that the microstructure and mechanical properties of A356 alloy can be significantly improved when ultrasonic cavitation and solidification processing is used. This is because during the fabrication of A356 castings, ultrasonic cavitation processing plays an important role in degassing and refining the as-cast microstructure. In the present study, A356 alloy and Al2O3/SiC nanoparticles are used as the matrix alloy and the reinforcements, respectively. Nanoparticles are injected into the molten alloy and dispersed by ultrasonic cavitation. Ultrasonic cavitation was also applied during solidification of these nanocomposites. The microstructure and nanoparticle distribution of the cast samples have been investigated in detail. The current experimental results indicated that ultrasonic cavitation during solidification will greatly improve the microstructure of the samples. Al2O3 and SiC nanoparticle reinforced nanocomposites have different nanoparticle distributions in the matrix.

The Effect of Iron Content on Microstructure and Mechanical Properties of A356 Cast Alloy

In the present study, microstructure and mechanical properties of A356 alloy including various amounts (0.2 to 1.2 wt pct) of iron were investigated. The alloys were produced by conventional gravity sand casting method. In order to determine the effect of iron addition to A356, optical and scanning electron microscopes (SEM/EDS) were used for microstructural examinations, and X-ray diffraction (XRD) analysis was carried out for phase characterization. Tensile tests were also conducted in order to determine effect of the Fe content on mechanical properties. It was found that as the Fe content of A356 was increased, the secondary dendrite arm spacing (SDAS) was decreased and the morphology of Al-Si eutectic became finer. From XRD examinations, different iron-based intermetallic compounds (β-Al5FeSi and α-Al8Fe2Si) formations were observed. It was also observed that as iron content increased, α-Al8Fe2Si intermetallic was transformed into β-Al5FeSi intermetallic. The tensile test results revealed that tensile strength and elongation values were reduced by increasing Fe content. It was also determined that β-Al5FeSi intermetallics were more negatively effective on tensile strength than α-Al8Fe2Si intermetallics.

The Effect of Modification and Grain Refining on the Microstructure and Mechanical Properties of A356 Alloy

The Effect of Modification and Grain Refining on the Microstructure and Mechanical Properties of A356 Alloy

Mg 첨가에 따른 A356 합금의 열처리 및 기계적 특성 변화

The effects of Mg addition on heat treatment and mechanical properties of A356 alloy were investigated. With increased amounts of Mg addition to A356 alloy, the grain size decreased and eutectic Si was refined. And, this process can improve the mechanical properties. Solid solution heat treatment causes the spheroidizing of eutectic Si. In this study, although eutectic Si was refined with Mg addition, solid solution time increased from 2 hours to 6 hours with Mg addition, and aging time also increased, from 4 hours to 8 hours. After heat treatment, Mg2Si remained in a formation of Chinese script. And, Chinese script Mg2Si formed with Mg addition caused a reduction of the elongation of the alloys according to the stress concentration.

Effect of TiN-Coated Al Powders on the Microstructure and Mechanical Properties of A356 Alloy

The core/shell nano-TiN-coated Al powders (TiN/Al) were prepared and added into A356 alloy by ultrasonic-assisted casting method in this work. The results show that TiN/Al has a better dispersion in A356 matrix and a stronger strengthening effect than TiN without the core/shell structure. With the addition of TiN/Al, most of the coarse primary α-Al dendrites of A356 turn into equiaxial. After T6 heat treatment, it is found that eutectic silicon in A356 with TiN/Al becomes columnar or globular in shape and smaller in size, which causes a greatly enhanced elongation of 11.7%. The results also suggest that the addition of nanoparticles can affect the precipitation behaviors and change the shapes and sizes of the precipitation.

The Effect of Scandium on the Mechanical Properties of A356 Aluminium Alloy

In this project, the addition of scandium (Sc) into A356 aluminium alloy was studied for its effect on the mechanical properties after gravity die casting process. Scandium addition was administered at the weight percentages of 0.1, 0.2 and 0.3. The results obtained in this work revealed that scandium can significantly enhance the mechanical properties of A356 alloy in terms of tensile strength, hardness and charpy impact strength. In general, the addition of 0.2 wt% Sc in A356 alloy was found to be able to achieve the maximum tensile strength of 172.94MPa as compared to 136.03MPa for sample without Sc. No significant improvement in tensile strength was found when more than 0.3wt% added to the alloy. As for hardness, the sample with 0.3 wt% Sc attained the maximum Vicker’s hardness of 86.60 HV as compared to 76.48 HV for unmodified A356. Similarly, the addition of 0.3wt% Sc in A356 can achieve highest impact energy of 2.71J as compare to 1.09J for unmodified A356.

Effect of Sc addition and T6 aging treatment on the microstructure modification and mechanical properties of A356 alloy

Effect of Sc addition and T6 aging treatment on the secondary dendritic arm spacing (SDAS), modification of eutectic Si morphology, β-Al5FeSiand π-Al8Mg3Si6Fe1 phases and its effect on mechanical properties in A356 alloy has been investigated. Addition of 0.4wt%Sc in A356 alloy resulted in a 50%reduction in the secondary dendritic arm spacing (SDAS). Sc addition changed the morphology of eutectic Si from plate like to fibrous and globular. The needle like morphology of β-Al5FeSi phase in A356 alloy changed to Al5Fe(Si,Sc) phase having smaller size and irregular morphology. Transmission electron microscopy (TEM) diffraction pattern and Energy dispersive spectroscopy (EDS) analysis revealed the presence of β-Al5FeSiand π-Al8Mg3Si6Fe1 phases in A356 alloy which changed to β-Al5Fe(Si,Sc), π-Al8Mg3(Si,Sc)6Fe1 and additional V-AlSi2Sc2phase was observed in Sc containing alloys. Addition of 0.4wt%Sc to A356 alloy improved its Vickers hardness, Ultimate tensile strength (UTS), Yield strength (YS) and ductility by 20%, 25%, 20% and 30% respectively. Artificial aging treatment resulted in significant improvement in the tensile properties for both A356 and Sc added A356 alloys.

Effects of Warm Laser Peening on Thermal Stability and High Temperature Mechanical Properties of A356 Alloy

To study the effects of warm laser peening (WLP) on the thermal stability and mechanical properties of A356 alloy, the samples were treated by WLP using a Nd:YAG solid-state laser and temperature control device. The residual stress, micro-hardness and microstructures of samples treated by WLP were observed. The result shows that the temperature significantly affects the strengthening effect of laser peening (LP). The residual stress induced by WLP decreases with the increasing temperature. The micro-hardness and dislocation density increase first, and then decrease with the increases of temperature. The grain refinement degree of the samples treated by WLP is much higher than that of LP. In addition, after aging for 100 min at 220 °C, the samples treated by LP and WLP were comparatively investigated in thermal stability. Obviously, the residual compressive stress, micro-hardness and microstructure induced by WLP present a better thermal stability property than that of LP. The residual stress and micro-hardness of WLP samples are obviously improved, and the increasing degrees are 23.31% and 19.70%, respectively. The dislocation density remains at a high level, while the grains are still in fine crystalline state.

Cooling Rate Sensitivity of RE-Containing Grain Refiner and Its Impact on the Microstructure and Mechanical Properties of A356 Alloy

The cooling rate sensitivities of AlTiB, RE and AlTiB–RE refiners were investigated using laboratory experiments and the actual industrial applications of A356 automotive wheel via low pressure die casting technology. Their impact mechanisms on the microstructure and mechanical properties of the A356 alloy were discussed. The results demonstrated that the AlTiB–RE refiner possessed most effective and synergetic refinement effects compared to the individual AlTiB or RE refiners. The AlTiB–RE refiner exhibited the least sensitivity to the cooling rate changes than the other refiners. The comprehensive properties of alloy wheel refined by the AlTiB–RE refiner were improved significantly. The tensile strength, yield strength, and elongation of wheel spoke improved by approximately 11.3%, 10.8% and 44.1%, respectively. The property difference values of the tensile strength, yield strength, and elongation in different positions of the wheel decreased from 14.8%, 31.2% and 47.7% to 8.6%, 27.1% and 30.9%, respectively.

Effect of Eu addition on the microstructures and mechanical properties of A356 aluminum alloys

The effect of Eu additions (0, 0.02, 0.04, 0.06, 0.08 and 0.1 wt.%) and T6 heat treatment on the microstructures and mechanical properties of A356 alloy have been investigated in the present work. Microstructures of the as-cast and T6 heat treated samples were examined by optical microscopy (OM) and scanning electron microscopy (SEM). It was found that 0.1%Eu modified the eutectic Si from a coarse plate-like form to a fully modified and fine fibrous one with a better uniform distribution. T6 treatment encouraged the spheroidization of eutectic Si particles. Correlating with the as-cast samples, the 0.1%Eu modified A356 alloy achieved likewise full modification of eutectic Si particles with lowest mean area and aspect ratio. In addition, the coarse and small Eu-rich intermetallics were both found in the 0.1%Eu modified A356 alloy. The cooling curves of A356 alloys showed that increasing Eu addition resulted in increasing nucleation undercooling and increasing growth undercooling. However, the recalescence (TG − TMin) increased by the initial addition of Eu, while it remained relatively stable for increasing additions (above 0.06%). The quenching experiment indicated that a large number of eutectic grains were located at or close to the tips of the aluminum dendrites with a jagged solid–liquid interface in unmodified alloy, while very few eutectic grains were formed in the interdendritic region with a smooth solid–liquid interface in 0.1%Eu modified alloy. An optimal combination of UTS (265 MPa) and EI (14.7%) of A356 alloy was achieved by the 0.1%Eu addition combined with T6 heat treatment.

Effect of Heat Treatment on Microstructures and Mechanical Properties of A356 Alloy by Low Pressure Casting

Automobile wheel of A356 alloy was cast by low pressure casting process. The effect of heat treatment process on microstructures and mechanical properties of A356 alloy cast was discussed. The results indicated that optimal parameters of heat treatment process for A356 alloy included solution temperature of 535°Cand holding time of 4.5hours, aging temperature of 145°Cand holding time of 4hours. Ultimate strength of A356 is 270MPa and elongation rate is 10%. Meanwhile, the microstructure has been apparently improved. The eutectic silicon particle became more spheroidal and distributed uniformly in matrix.

Characteristics of mold filling and entrainment of oxide film in low pressure casting of A356 alloy

The effect of pressurizing speed of low pressure casting on mold filling and mechanical properties of A356 alloy was studied. The mold filling behavior was calculated by two phase flow model using VOF (Volume of Fluid) method. In order to evaluate the accuracy of simulated results, the real mold filling process observed by X-ray radiography was compared. The results show that during mold filling the gate velocity first increased dramatically, then kept unchanged under relatively low pressurizing speed, or increased slowly under relatively high pressurizing speed. High gate velocity causes melt falling back under gravity with high speed. The falling velocity and the resultant relative rotating vortex are the main causes of oxide film entrainment in low pressure casting. The mechanical properties of the as-cast A356 alloy were measured by four-point bend test. Weibull probability plots were used to assess the fracture mechanisms under different pressurizing speeds. The results obtained in this paper illuminate on designing suitable pressurizing speed for mold filling in low pressure casting.

The effects of scandium on A356 aluminium alloy in gravity die casting

In this project, the addition of scandium into A356 aluminium alloy was studied for its effect on the mechanical properties as well as the changes in microstructure and eutectic morphology after casting process. Scandium addition was administered at the weight percentages of 0·2, 0·4 and 0·6. The results obtained in this work revealed that scandium can significantly enhance the mechanical properties of A356 alloy in terms of hardness and tensile strength. In general, the addition of 0·4 wt-% scandium in A356 alloy was found to be able to achieve the maximum tensile strength of 119·48 MPa as compared to 91·36 MPa for sample without scandium. Similarly, the sample with 0·4 wt-% scandium attained the maximum hardness of 20·36 HRA as compared to 17·32 HRA for unmodified A356. The mechanism that renders the enhancement in mechanical properties can be attributed to grain refinement. In SEM micrographs of samples with scandium, grain refinement can be observed in the microstructure and the morphology of eutectic structure. The eutectic morphology was also converted into a finer and fibrous structure.