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solid metal (SSM) processing is a relatively successful method for forming alloys in the semi-solid state to near net shaped products. One type of SSM processing is thixoforming which is used widely in the automotive industry to produce near net-shaped parts. All the alloys that have been used to date for thixoforming were developed originally for...
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... solidification temperature ranges of A319 and modified A319 are shown in Fig. 6. For A319, the solidification temperature is 149.9K whereas for alloys A, B, C and D, the corresponding temperature is 129.8K, 131.3K, 132.6K and 133.8K, respectively. These temperatures show good agreement with the alloys design criterion which specifies that the solidification temperatures should be less than 150K. All alloys with a ...
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... The main tool used to assess thixoformability is the solid fraction vs. the temperature (f S vs. T) curve of the alloy in the semisolid state. This can be determined by CALPHAD (Calculation of Phase Diagrams) simulation [4,[10][11][12][13][14] (at equilibrium/near-equilibrium conditions for solidification) or experimentally (far from equilibrium conditions and during melting) by techniques such as differential scanning calorimetry (DSC) using low-mass samples (of the order of milligrams) to provide rapid, reliable measurement of the heat flow variations associated with the semisolid transformations [4,[10][11][12][13][14]. In this paper, the effects of Si content (X = 4-7 wt.%), heating rate (5-25 • C/min) and sample mass (20-200 mg) on determination of the thixoforming working window by DSC are analyzed for the Al-Xwt.%Si-4wt.%Zn ...
... The main tool used to assess thixoformability is the solid fraction vs. the temperature (f S vs. T) curve of the alloy in the semisolid state. This can be determined by CALPHAD (Calculation of Phase Diagrams) simulation [4,[10][11][12][13][14] (at equilibrium/near-equilibrium conditions for solidification) or experimentally (far from equilibrium conditions and during melting) by techniques such as differential scanning calorimetry (DSC) using low-mass samples (of the order of milligrams) to provide rapid, reliable measurement of the heat flow variations associated with the semisolid transformations [4,[10][11][12][13][14]. In this paper, the effects of Si content (X = 4-7 wt.%), heating rate (5-25 • C/min) and sample mass (20-200 mg) on determination of the thixoforming working window by DSC are analyzed for the Al-Xwt.%Si-4wt.%Zn ...
... In order to understand how the trends observed in the DSC curves affect the thixoforming working window (∆T THIXO ) [6], the analysis applied to the DSC data is shown schematically in Figure 5 in the following order: starting with the original HFR curve (black curve in Figure 5a), the derivative of the HFR curve with respect to T is plotted (red curve in Figure 5a) and the temperatures of the beginning (T SSML ) and end (T SSMH ) of ∆T THIXO are determined using a baseline = 0 established by the differentiation method (DM) [10]. Using the solidus and liquidus temperatures (also obtained by the DM), the limits of integration of partial areas between the DSC curve and the baseline are set and the f S vs. T curve (blue curve in Figure 5b) is drawn [12]. The positions on the f S curve corresponding to T SSML and T SSMH on the dHFR/dT vs. T curve provide the solid fractions corresponding to these temperatures, i.e., fs SSML and fs SSMH (Figure 5c). ...
The effects of Si content (X = 4 to 7 wt.%), heating rate (5 to 25 °C/min) and sample mass (20 to 200 mg) on determination of the thixoforming working window by differential scanning calorimetry DSC were analyzed for the Al-Xwt.%Si-4wt.%Zn, or simply AlXSi4Zn, system. The critical lower and upper temperatures for thixoforming processing were determined by applying the differentiation method to DSC heating cycle data. Lower Si content, heating rate and DSC sample mass made identification of the working window temperatures more accurate because of the sharpening of the DSC curve when lower values of these variables were used. Data obtained when lower sample masses and heating rates were used agreed better with those obtained by Calculation of Phase Diagrams, (CALPHAD) simulation (near-equilibrium Scheil condition) for all the Si contents analyzed. Larger DSC sample masses were associated with significant heterogeneity in heat transfer through the sample, leading to results similar to those for a diffuse transition, an effect enhanced by an increase in the heating rate. Since Si content represented a limitation when identifying the working window by the differentiation method, alloys with high Si content should be analyzed with lower DSC masses and lower heating rates to allow more accurate determination of the interval at conditions near those used in thixoforming operations.
... This type of alloy offers a high degree of strength with excellent castability, light weight and good machinability [1,2]. The microstructural constituents present in this alloy are typically complex multiphase comprising eutectic Si and also numerous intermetallic phases such as Al 2 Cu, Mg 2 Si, Al 9 FeMg 3 Si 5 , β-Al 5 FeSi and Al 5 Cu 2 Mg 8 Si 5 [3,4]. In recent years, the need to produce near net-shape products that have superior properties to those produced by the conventional casting process has drawn attention towards a new processing technique known as semi-solid metal (SSM) processing [5]. ...
The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.
... SSM processing promotes a solution to the problems associated with die casting due to its capability to use temperature lower than those used in die casting, [6] and also used low forming forces during the shaping process [7]. Among the SSM processing techniques, cooling slope (CS) is one of the suitable techniques to obtain fine globular primary particles with a high degree of sphericity [8]. ...
Aluminium alloys are among the most prominent and well known materials used in automotive industries. Nowadays, many vehicles used aluminium engine blocks instead of cast iron to improve fuel efficiency. Among cast aluminium alloys, A319 grade alloys are normally used in automotive industries due to a combination of good fluidity and mechanical strength. In this study, A319 cooling slope rheocasting billets were produced in order to obtain near spherical morphology of primary aluminium phase. The change in the α-Al morphology upon the cooling slope casting was remarkable and the dendritic microstructure was almost replaced by α-Al globules and rosettes. The rheocasting billets were prepared for tensile testing at room temperature. It is found that, the yield strength and elongation of cooling slope rheocasting billets is higher than those from as-cast A319 alloy.
... Ini menunjukkan kandungan 7.5 %bt tembaga adalah maksimum untuk aloi A319 dalam mengawal pecahan cecair agar berada dalam julat 30 dan 50% pecahan cecair seperti yang telah dibincangkan. Peningkatan %bt elemen tembaga dalam aloi A319 juga dapat mengurangkan suhu pemprosesannya iaitu 558°C untuk 3.5 %bt kandungan tembaga, 553°C untuk 5.5 %bt kandungan tembaga dan 548°C untuk 7.5 %bt kandungan tembaga seperti ditunjukkan dalam Rajah 6. Pengurangan suhu pemprosesan ini dapat memanjangkan lagi jangka hayat acuan melalui pengurangan kejutan terma yang berlaku pada acuan semasa proses pembentukan-tikso (Salleh et al. 2013). ...
Thixoforming is a new technology in producing near net-shape products in semisolid state. This process can reduce macrosegregation, porosity and involve low forming forces. Currently, there are a few grades of aluminum alloys such as A319, A356 and A357 commonly used in semi-solid metal processing. Therefore, there is a demand to widen the range of aluminum alloys specially tailored for semisolid metal processing. This study discusses the thermodynamic modelling to predict changes in the properties of aluminum alloy A319 expecially when the content of alloying elements such as copper, manganese and iron are varied in order to fulfill the criteria of semisolid metal processing. All the calculations in the present work were performed using Java-based Material Properties (JMatPro) commercial software. Thermodynamic calculation based on Scheil’s equation is used to determine solidification temperature range (ΔT), liquid fraction sensitivity (dfL/dT) and processing window temperature (ΔT30/50). The thermodynamic calculation shows that the solidification temperatures have decreased from 130 to 113°C while the eutectic temperatures have increased from 510 to 515°C when the wt.% of copper, manganese and ferum were increased. The liquid fraction sensitivity is reduced from 0.017 to 0.007°C-1 and the processing window temperature is reduced from 26 to 24°C. Eutectics binary reactions occurred between 30 and 50% liquid fraction for all alloy groups. Phase diagram is used to identify the formation of intermetallic phase compound such as β-Al5FeSi and Al2Cu in the alloys. The results indicate the suitability of these modified alloys as potential materials for semisolid processing.
... Numerous studies have been performed over the last 14 years on SSM processing. Over the past few years, there has been extensive interest in the development of new alloys and also modified commercial alloys specially tailored for SSM processing [1] [2]. Today, this process has become an important manufacturing technology used to produce engineering components. ...
A319 aluminum alloys are commonly used in automotive industry due to a combination of good fluidity and mechanical strength. In this present work, cooling slope (CS) rheocasting process was employed to produce A319 billets with near spherical morphology of primary Al phase. The dendritic primary phase in the cast A319 alloy had readily transformed into nondendritic when the ingots were cast over a cooling plate from pouring temperatures between 620°C and 640°C and with cooling lengths of between 300 mm and 400 mm. The shear driven flow of the solidifying melt on the cooling slope wall promotes heterogeneous nucleation of α-Al phase and subsequent separation from there due to shear driven flow of the solidifying melt produced nearly spheroidal morphology of the primary phase in the microstructure. The results show that the best combination of pouring temperature and cooling length was found to be 630°C and 400 mm respectively. The hardness of the rheocast ingots improved to 85.3 HV from 81.8 HV in as-cast condition.
... One type of SSM processing is thixoforming which involves the preparation of suitable feedstock alloys followed by re-heating to semi-solid states before forming to near net shaped products [5]. Over the years, there has been extensive interest in the development of new alloys specially tailored for SSM processing [6][7][8]. ...
In this study, the effects of copper content on the microstructures and tensile properties of thixoformed Al-5Si-xCu-0.5Fe (x =1.0, 2.0 and 3.0wt. %) were investigated. For this study, three different alloys having various amounts of copper were prepared using cooling slope casting before thixoforming. The semi-solid liquid range for the alloys were estimated using the diffrential scanning calorimetry (DSC) analysis. The samples were thixoformed at 40% liquid fraction. Some of these samples were treated with a T6 aging process. The thixoformed and thixoformed T6 samples were then characterized by optical microscopy, scanning electron microscope (SEM) and energy dispersive X-ray (EDX) as well as tensile tests. The different phases formed in the thixoformed and thixoformed T6 samples were throughly investigated.The results indicate that as copper content increases, the tensile strength also increases, which might due to precipitation hardening. The thixoformed T6 alloys attained an ultimate tensile strength (UTS) as high as 303 MPa when Cu content is 3.0wt.%.
... Semisolid forming has many advantages, such as complex shapes can be formed with some reduction in forming steps and with near net shaping capabilities, less energy consumption, less solidification shrinkage, prolonged die life, good filling of the die and improved mechanical properties [7,8]. The production of raw material for semisolid processing requires specialized techniques such as mechanical stirring, inductive electromagnetic stirring and the cooling slope method. ...
In this study, A356/Al 2 O 3 metal matrix composites were fabricated by conventional stirring and semisolid processing (combination of mechanical stirring in the mushy zone and cooling slope casting) and these composites were subjected to wear tests. The composites containing various weight fractions of Al 2 O 3 particles (1%, 2.5% and 5%) were used in both conventional and rheocasting processes. In conventional stirring, the primary phase remained dendritic while in rheocasting the dendritic primary phase transformed into a globular microstructure. The influences of these processes on the hardness and wear behaviour of the composites were investigated. A pin-on-disc tribometer was used to carry out tribological tests under dry sliding conditions in air. Wear tests were carried out at 1.0 m/s sliding speed under a 20N load and four different sliding distances. A scanning electron microscope was used to examine the wear mechanism on the worn surfaces of the composites. The results showed that the volume loss of the composites produced by semisolid processing was lower than that of those produced by conventional casting. Based on wear rate ranges, all metal matrix composites exhibited moderate wear regimes. The dominant wear mechanism for all materials was ploughing, with some delimitation.
This paper presents numerical models that are able simulate a buckling of the rubber boot. Rubber boot must be able of a large change of its length. A buckling of cylindrical shape of the boot during this deformation would cause a serious problem. Due to the space limitation in an assembly it is quite difficult to find optimal shape of the boot profile which will be able of the required deformation without the buckling. We have created numerical models that are able to simulate mechanical behavior of the compressed boot including the buckling of the boot with an inappropriate profile. Due to the material of the boot (rubber), a nonlinear hyperelastic material model was used in the analyses. The material constants of this hyperelastic model were obtained from the uniaxial and equibiaxial tests of the boot material. Created numerical models were used to design the optimal shape of the boot which eliminates the risk of the buckling.
The goal of this work is to create numerical model, which will be used for design and optimization of a rubber bushing of stabilizer bar. Thanks this model we are able to predict the mechanical behavior of the bushing. To get material constants for the model, the material of bushing (rubber) was tested in special deformations modes. A hyperelastic material model was set and it was implemented into the numerical model of the bushing. Critical points in the construction of bushing were reveled by the analysis of the numerical model.
In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al-5%Si-Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 hours, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 hours. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π- Al9FeMg3Si5 phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt% Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed.
