Mechanical Properties Of A356 Alloy Research Articles

Effect of Al-Sr-Y intermediate alloy on microstructure and mechanical properties of A356 alloy

In this experiment, an intermediate alloy (Al-3Sr-8Y) that can refine and modify A356 alloy simultaneously was developed, and the synergistic effect of Sr and Y on the microstructure and mechanical properties of A356 alloy was investigated. The results show that when the content of Al-3Sr-8Y intermediate alloy reaches 0.3 wt%, the morphology of α-Al dendrites is significantly refined and the secondary dendrite arm spacing (SDAS) was significantly reduced. Moreover, the morphology of eutectic Si transforms from acicular to small fibrous, and the average area and aspect ratio of eutectic Si decrease to 0.81 μm2, and 2.01. This change is caused by the twin plane re-entrant edge (TPRE) poisoning mechanism, where the addition of Al-3Sr-8Y can poison the intrinsic growth position of the Si phase, reduce the growth rate of the Si phase, promote isotropic growth, and achieve a highly branched morphology of the Si phase to form a fibrous structure. Due to the excellent synergistic effect of Sr and Y, the tensile strength and elongation of the alloy reached the maximum values of 303.5 MPa and 9.5% when 0.3 wt% Al-3Sr-8Y was added after heat treatment, which is an increase of 18.2% and 86.3% compared with the untreated A356 alloy, respectively.

Response of mechanical properties of A356 alloy to continuous rheological extrusion Al-5Ti-0.6C-xCe alloy addition upon different Ce contents

A356 alloy is a commonly used casting Al-Si alloy. Because of the excellent fluidity, air-tightness and thermal resistance, it is usually used as castings with complex structure. However, due to the coarse α-Al grains and needle-like phases, the defects including shrinkage cavity and porosity can easily be formed, which reduce the mechanical properties of the castings and lead to the lower safety factor. In this paper, Al-5Ti-0.6C-xCe (x = 0, 0.5, 1.0, 1.5 and 2.0 wt%) master alloys have been prepared by fluorine-salt method combined with the continuous rheological extrusion (CRE) technology. The response of mechanical properties of A356 alloy to the CRE Al-Ti-C-Ce alloys addition upon different Ce contents was investigated. Results showed that, with the increasing Ce content from 0 to 2.0 wt%, the average grain size of α-Al and length of coarse needle-like phases in A356 alloy changed nonmonotonically. When the Ce content was 1.0 wt%, the best refined structure was obtained. The tensile strength, yield strength and elongation of refined A356 by CRE Al-5Ti-0.6C-1.0Ce master alloy were 290.45 MPa, 238.27 MPa and 2.80%, respectively. The introduction of master alloys with different Ce contents promoted the refinement of grain and coarse needle-like phase in A356 alloy, which further improved the mechanical property of the alloy.

Mechanical Properties of Refined A356 Alloy in Response to Continuous Rheological Extruded Al-5Ti-0.6C-1.0Ce Alloy Prepared at Different Temperatures

The microstructure is an important factor determining the mechanical properties of A356 alloy. In this experiment, the refiner Al-5Ti-0.6C-1.0Ce master alloys under different preparation temperatures were prepared, and the A356 alloy was refined. The effects of preparation temperature on the number and morphological distribution of each phase in Al-Ti-C-Ce master alloy and the effects of Al-Ti-C-Ce master alloy at different preparation temperatures on the microstructure and mechanical properties of A356 alloy were explored successively. Results showed that, as preparation temperature increased from 850 to 1150 °C, TiAl3 changed from large blocks to long strips and a needle-like phase, and Ti2Al20Ce changed from a bright white block to a broken small block phase. Al-5Ti-0.6C-1.0Ce prepared at 1050 °C can significantly refine the α-Al of A356 alloy and modify eutectic Si. The α-Al grain size was refined from about 1540 to 179.7 μm, and the eutectic Si length was refined from about 22.3 to 17.8 μm with the transition from a coarse needle-like to a short rod-like structure. The ultimate tensile strength and elongation of A356 alloy changed non-monotonically, and the peak values were 282.216 MPa and 3.9% with the Al-Ti-C-Ce preparation temperature of 1050 °C and 950 °C, respectively.

Enhancing Fe content tolerance in A356 alloys for achieving low carbon footprint aluminum structure castings

Low carbon footprint aluminum structure castings are the mainstream development direction of aluminum alloys in the future. Enhancing the Fe content tolerance upper limit in casting aluminum alloys is considered an effective way to promote the application of recycled aluminum production. In this work, it was found that with the Ce and TiCN NPs (nanoparticles) addition simultaneously to A356 alloys, the acicular Fe-rich phases (β-Al5FeSi) which damages the properties can be changed into beneficial phases (core-shell heterostructures) for the alloy, and hence the mechanical properties of A356 alloys can be improved. The TiCN nanoparticles and rare element Ce play crucial roles in the formation of core-shell heterostructures. The formation mechanism of core-shell heterostructure was also systematically researched from the perspective of thermodynamics and kinetics. This study provides a simple and feasible strategy to eliminate the harmful effects of Fe impurity and contributes to the industrialization of low carbon footprint aluminum structure castings.

Investigation of Phase Transformation and Mechanical Properties of A356 Alloy with Cu and Zr Addition during Heat Treatment

Cast A356(Al-Si-Mg) alloys are widely used in automotive and general applications because of their mechanical properties and castability. Al-Si-Mg-(Cu) alloys typically lose their strength above 170 o C due to coarsening of precipitates, which limits their application to components. To maintain their strength at elevated temperature, Al-Si-Mg-(Cu) alloys are modified by adding transitional metals. Several studies have been carried out to evaluate the effect of Zr addition on the high temperature mechanical properties of cast Al-Si alloys because Zr can form thermally stable phases such as Al3Zr. Despite the relative studies on the influence of Cu and Zr on the mechanical properties of cast Al-Si-Mg-(Cu) alloys, investigations of the effect of Zr on the phase transformations and the mechanical properties during heat treatment remains limited. In this study, the effects of added Cu and Zr on the phase transformations and the mechanical performance during heat treatment of A356 cast alloy were investigated. Needle-like and block-like (Al,Si)3(Ti,Zr) dispersoids formed as some Si and Ti replaced Al and Zr in Al3Zr crystal structures were generally observed. Furthermore, with increasing solution treatment time, the size of Zr dispersoids was reduced, and smaller Zr particles were precipitated at the same time, which caused a decrease in the area fraction of the Zr dispersoids. In addition, the metastable L12 structures of Zr dispersoids in Al-Si-Mg-Cu-Zr alloys were transformed into stable D023 during solution heat treatment as the Cu addition accelerated the transformation. Tensile and low-cycle fatigue (LCF) tests were performed to reveal the effects of (Al,Si)3(Ti,Zr) dispersoids on mechanical properties. As a result, elongation at elevated temperature was highly increased, while maintaining strength, according to the increase in solution heat treatment time, which improved low-cycle fatigue properties.

Effect of stirring speed and temperature on the microstructure and mechanical properties of A356 alloy under vacuum

In this work, an effective method was proposed to purify aluminum alloy melt under stirring and vacuum. The formation mechanism of pore defects and their effects on the mechanical properties of A356 alloy were investigated. The results showed that compared with the untreated alloy, the mechanical properties of the purified A356 alloy were significantly improved. The purification parameters, including stirring speed and stirring temperature, had crucial effects on determining the size of dendrites and pores. The optimized stirring speed and stirring temperatures were 65 rpm and 730 °C, respectively. In this condition, grains with an average diameter of 279 μm and pores having an average diameter of 79.5 μm were obtained; the ultimate tensile strength, yield strength and elongation of the purified alloy reached 203.7 ± 4.3 MPa, 81.6 ± 3.3 MPa and 10.2 ± 0.5%, respectively. The variation in the microstructure and mechanical properties was associated with the bubble breakup mechanism, which accelerated the removal of bubbles in the melt during stirring in vacuum. Furthermore, the interaction between pore and solidified microstructure was also discussed.

The Application of the Direct Water Cooling Process on the Lost-Foam Casting Technique to Improve Microstructural and Mechanical Properties of A356 Alloy

The Application of the Direct Water Cooling Process on the Lost-Foam Casting Technique to Improve Microstructural and Mechanical Properties of A356 Alloy

Microstructures and Mechanical Properties of A356 Alloy and A6061 Alloy through Rheo, Upsetting, Thixo, Forming Process, and T6 Heat Treatment

The thixo process has the benefit of producing a semi-solid material in which fine primary α-Al grains are uniformly distributed. However, it also has the disadvantage of a costly raw material billet. In this study, a semi-solid slurry was prepared from the rheo process by cooling and electromagnetic stirring, and then a billet for the thixo process was manufactured through an upsetting process with semi-solid slurry. Then, the billet was reheated (thixo process) to make a semi-solid state, and then a final sample was manufactured through a forming process. In both A356 and A6061 materials, the equivalent diameter of the primary α-Al grains became smaller and the roundness became close to one throughout rheo, upsetting, thixo, and forming processes. Due to the refinement and spheroidizing effect of the primary α-Al grains, the tensile strength was improved by each process, and the elongation was slightly decreased. However, after T6 heat treatment, the tensile strength of A356 was decreased, but the elongation was greatly improved. In the case of A6061, on the other hand, the tensile strength was significantly improved, and its elongation decreased after T6 heat treatment.

Effect of Sr–Ce modification on the microstructure and mechanical properties of A356 alloy

Effect of Sr–Ce modification on the microstructure and mechanical properties of A356 alloy

New technique for preparing A356 alloy semisolid slurry and its rheo-diecast microstructure and properties

A new technique for preparing semisolid slurry, namely, distributary-confluence runner (DCR), was combined with die-casting (DC) to conduct rheological die-casting (R-DC) of A356 alloy. The mechanism of DCR for semisolid slurry preparation was determined via numerical simulations and experiments. The microstructure and mechanical properties of A356 alloys prepared via DC and R-DC were studied. High-quality slurry containing numerous primary α-Al (α1-Al) with an average size of 49 μm and a shape factor of 0.81 could be prepared via DCR. Simulation results indicated that the unique flow state and physical field changes during slurry preparation were conducive to accelerating the uniformity of melt temperature and composition fields, nucleation exfoliation, and spherical growth. Compared with the alloy prepared via DC, the tensile strength, yield strength, and elongation of A356 alloy prepared via R-DC increased by 19%, 15%, and 107%, respectively.

Effects of Ti particles and T6 heat treatment on the microstructure and mechanical properties of A356 alloy fabricated by compocasting

In this study, the effects of the addition of Ti powder and T6 heat treatment on the microstructure and the mechanical properties of A356-based composite containing 0.5, 1.5, and 5 wt% Ti fabricated by compocasting were studied. Stirring was carried out at a temperature of 610 °C with a stirring speed of 300 rpm for 10 min. The solution treatment was done at a temperature of 540 °C for 2 h. Then, age hardening was conducted at 170 °C for 7 h. The microstructures and mechanical properties of samples after T6 heat treatment were investigated. After the addition of titanium powder, a reaction layer created on the surface of the titanium powder by diffusion of Ti atoms across the Al melt/Ti interface. Increasing the weight percent of the Ti particles resulted in an increment of silicon nucleation and a decrement of the silicon size. Also, the porosity content increased with increasing the weight percent of Ti. The eutectic Si structure was transformed from a coarse needle-like structure to a short plate-like one by T6 heat treatment. Among all samples, the A356/0.5 wt% Ti composite after the T6 showed the highest ultimate tensile strength (UTS) (306.9 MPa). Compared to the A356 alloy, the hardness and tensile strength of the A356/0.5 wt% Ti composite improved more than 83% and 53%, respectively, due to the presence of Ti and Al3Ti phases. For the A356/Ti composites, the fracture surface was mainly covered by cleavage features.

Effects of thermal-rate treatment and modification of Ce on the microstructure and properties of A356 alloys

In this study, the effects of thermal-rate treatment (TRT) and modification of Ce on the microstructure and mechanical properties of A356 alloy were investigated. The results showed that the microstructure of A356 alloy was improved after TRT and modification of Ce. The α-Al was refined significantly and the eutectic Si transformed from needle-like shape to granular-like shape. When the content of Ce increased to 0.5%, the grain size of α-Al of A356 alloy began to increase and the dendrites became coarse. When the Ce content was 0.4%, the tensile strength and yield strength of A356 alloy were 183MPa and 124 MPa, respectively. The mechanism of (TRT+Ce) on the grain refinement of α-Al and modification of eutectic Si was discussed.

Effect of Al-3 wt% Al2O3 master alloy fabricated by calcined kaolin on grain refinement and mechanical properties of A356 alloy

In the present study, Al-3 wt% Al2O3 master alloy was successfully prepared by the reaction between calcined kaolin and aluminum melt, combined with mechanical stirring and high-energy ultrasonic dispersion technology. The γ-Al2O3 particles produced by the reaction are uniformly dispersed in the matrix, and the average size of γ-Al2O3 is about 65 nm. The refinement effect of Al-3 wt% Al2O3 master alloy on A356 alloy was studied. It was found that the α-Al grain size in A356 alloy refined by Al-3 wt% Al2O3 master alloy was decreased from 980 ± 155 µm to 337 ± 95 µm. Compared with the Al-5Ti-1B master alloy, Al-3 wt% Al2O3 has a higher refinement efficiency. In addition, the refinement efficiency of the Al-3 wt% Al2O3 master alloy will not fade within 60 min. Transmission electron microscope analysis showed that the orientation relationship between γ-Al2O3 and Al was (22−2)γ-Al2O3[011]γ-Al2O3//(11−1)Al[011]Al, which demonstrated that γ-Al2O3 could be used as heterogeneous nucleation sites to refine α-Al grains. Moreover, the tensile properties of A356 alloy had been significantly improved.

Effect of Ti addition holding time on casting quality and mechanical properties of A356 alloy

Bifilms are casting defects that occur due to the incorporation of surface oxide film into the melt. Thus, they act as a crack in the liquid. Once they remain in the structure, they decrease mechanical properties owing to their negative effect on porosity formation. One of the most fundamental problems to be avoided in this frame is the reduction of the bifilms or the cleaning of the liquid metal to prevent the porosity formation. In this study, A356 (Al–7Si–0.3 Mg) alloy was used. AlTi5B1 master alloy was added as a grain refiner. The effect of Ti on casting quality and mechanical properties changes by holding time was evaluated. The results were examined statistically by Weibull analysis. It was found that the presence of bifilms can be reduced as holding time increases after adding Ti. The tensile properties were increased as the holding time increased. Additionally, the optimum holding time may be 40 min after Ti addition for high casting quality and good mechanical properties.

The Effect of Holding Time After Sr Addition on Microstructural and Mechanical Properties of A356 Alloy

The spheroidization of the silicon eutectic phase in aluminum is an important parameter for casting and significantly influences the material properties. Sr has been used for a long time for eutectic modification in aluminum and many researches have been made on this subject. In this study, the effect of holding time after Sr addition on the mechanical properties and eutectic phase modification of the aluminum were investigated. 200 ppm Sr was chosen as the amount of Sr and the holding times were chosen as 20, 40 and 80 minutes. Tensile test was performed for the determination of mechanical properties and ultimate tensile strength and percentage of elongation values were measured. In order to quantify eutectic modification, the length / width (aspect ratio) ratios of eutectic silicon particles were measured. In addition, Bifilm Index of the molten metal was determined with the reduced pressure test (RPT). With the increase in the holding time, an increase in the aspect ratio and in the Bifilm Index was measured. It has been observed that the tensile strength and elongation values have decreased as the holding time has increased.

The Effects of Cr and Zr Additives on the Microstructure and Mechanical Properties of A356 Alloy

This study has investigated the effect of different amounts of Cr and Zr additions on the microstructure and mechanical properties of A356 alloy modified with strontium. The microstructure and phase examination were performed using an optical microscope, scanning electron microscope and XRD analysis, whereas mechanical properties were investigated via tensile testing and hardness measurements. Two-dimensional Weibull distribution was used to determine the effect of Cr and Zr additions on mechanical properties of A356 alloy. It was found that the most significant effect of Cr and Zr added was over the morphology of Al–Si–Fe intermetallics. The addition of Cr and Zr led to the formation of Cr/Zr-based intermetallics in precipitates and fish-bone-like morphologies. It was observed that increasing the amount of Cr and Zr had resulted in an increase in ductility of A356.

Effects of Al-5Ti-0.62C-1.07La intermediate alloy on the microstructure and mechanical properties of A356 aluminum alloy

The physical characters that belong to hypo-eutectic Al-Si alloys are affected by certain important factors including the dimension, distribution together with structure of eutectic Si crystals together with primary α-Al. In this paper, A356-x Al-5Ti-0.62C-1.07La (x = 0, 4, 5, 6, 7 wt%) alloys are was prepared by mechanical stirring. The effects of Al-5Ti-0.62C-1.07La intermediate alloy on the microstructures and mechanical properties of A356 alloy are investigated. Results show that the primary α-Al was significantly refined by Al-5Ti-0.62C-1.07La intermediate alloy. The secondary dendrite arm space (SDAS) of unrefined α-Al is approximately 40 μm. When the substance of Al-5Ti-0.62C-1.07La intermediate alloy is 6 wt%, SDAS declines to 10 μm. In addition, the component part of eutectic Si turns from thick acicular/schistose to short rod-like together with a section of pellets. Adding 6 wt% Al-5Ti-0.62C-1.07La intermediate alloy, A356-T6 alloy obtained the best tensile function and hardness. The ultimate tensile strength (UTS), elongation (El) together with Vickers hardness (HV) are 183.5 MPa, 8.2% and 62.3, which is increased by 30.3%, 95.2% and 38.1%, respectively. Furthermore, the variation in mechanical properties change with the development of micro-structure.

Grain Refining Effect of Al-5Ti-1B Master Alloy on Microstructures and Mechanical Properties of A356 Alloy

In this study, the structures of Al-5Ti-1B master alloy and its influence on microstructures and mechanical properties of A356 alloy were investigated. The results show that Al-5Ti-1B master alloy consisted of the uniform distribution of lump-like TiB2 and network of TiAl3 on α-Al matrix. The addition of the Al-5Ti-1B master alloy can significantly reduce the grain size of A356 alloy. The mechanical properties of A356 alloy, i.e. ultimate tensile strength, yield strength and elongation were also improved. The use of Al-5Ti-1B master alloy as a grain refiner in the casting process of A356 alloy can effectively enhance the grain refinement and thus improve the mechanical performance of A356 alloy.

Microstructural and Mechanical Characteristics of A356 Alloys as a Function of Mn Content and Cast Thickness.

In this study, the changes in the microstructural characteristics and mechanical properties of A356 alloys as a function of Mn content and cast thickness were evaluated using structural analysis and tensile tests. Five different A356+x%Mn alloys were prepared by casting in molds of different thicknesses followed by solid solution treatment at 813 K for 195 min and aging treatment at 423 K for 120 min. It was confirmed that the secondary dendrite arm spacing (SDAS) increased with increasing thickness of the cast sample, whilst, for a given thickness, the addition of small amounts of Mn resulted in a decrease of the SDAS. Mn contents of 0.05-0.15% resulted in ~7-9% improvements in the spheroid ratio of the primary Si particles compared to that of the commercial A356 alloy. Further, the spheroid ratio of the primary Si particles obtained in the thin cast samples were higher than that obtained in the thick cast samples. In particular, the addition of small amounts of Mn was also effective in suppressing the formation of the needle-like beta Al-Fe-Si intermetallic compound. The yield and tensile strengths of the thinner cast samples were higher than those of the thicker cast samples. Finally, Mn contents of 0.05-0.15% resulted in enhanced yield and tensile strengths, but Mn content ≥0.1% resulted in decreased elongation.

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.