Papers by Keyword: Hypereutectic Al-Si Alloy

Abstract: In order to settle environment pollution and provide a high effective and low-cost modifier for refining the primary Si in hypereutectic Al-Si alloys, Al-Fe-P master alloys containing 2.0~5.0% phosphorus have been invented by casting method. The Al-Fe-P master alloys can be conveniently produced and an excellent modification can be obtained by adding 0.3~0.8wt% Al-Fe-P master alloy in Al-Si alloys containing 12%-25% Si at a relatively lower modifying temperature. The number of primary Si increases obviously and the average grain size of primary Si decreases largely, less than 50μm. Furthermore Al-Fe-P master alloys have many advantages, such as low cost, convenient operation technology, no pollution, stable and long-term modification effect, easy storage and etc. Al-Fe-P master alloys have overcome the shortages of current modifier and have a good future for hypereutectic Al-Si alloy modification.

Abstract: The hot deformation behavior of hypereutectic aluminium-silicon alloy was investigated by thermal simulation test at the deformation temperature of 330-480 and the strain rate of 0.1-10s^-1 using the Gleeble-1500 thermal mechanical simulator. The relationship of flow stress, temperature and strain rate was appropriately described by the deformation constitutive equation, and the deformation activation energy is 187.418 KJ/mol. In addition, the microstructures of these specimens were analyzed and the result showed that the inhomogeneous deformation enhances with increasing strain rate and decreasing deformation temperature, and the presence of primary silicon had a strong influence on the uneven deformation.

Abstract: Mg2Si particle reinforced hypereutectic Al-Si composite was prepared by casting, and the microstructure and wear resistance of the composite were researched. The results indicated that the morphology of Mg2Si obviously changed with Mg2Si contents increasing, in which the morphology of Mg2Si in the composite had changed from polygon block to characters like and finally became coarse dendrite. There were effects of Mg2Si content and morphology on the wear resistance in the composite, which had the higher hardness and better wear resistance at the suitable Mg2Si content.

Abstract: Mg2Si reinforced hypereutectic Al-Si composite was prepared and the effects of electro- magnetic stirring on Mg2Si particle in the composite were researched. The results indicated that there were the important effects of electromagnetic stirring on size and morphology of the particle in the composite. The morphology and size of the particle in the composite were obviously improved by electromagnetic stirring. In comparison with the sample without isothermal holding, the size of the particle isothermally held slightly increased under the same stirring condition, but the roundness of the particle was improved. After isothermal holding, the mechanical properties of the composite prepared by electromagnetic stirring were improved to some extent.

Abstract: Semisolid forging process, characterized by short process, near-net shape, low cost, and high performance, is increasingly playing an important role in lightweighting transportation systems for light metals. In this study, semisolid forging process for hypereutectic Al-Si alloy, as a substitute for nodular cast iron, was applied in producing automobile AC compressor components. The results showed that hypereutectic Al-Si alloy swash plate thixo-forged had higher strength than nodular cast iron one by optimizing forming process parameters.

Abstract: The microstructure and mechanical properties of Al-17Si-2Fe-2Cu-1Ni (mass fraction, %) alloys with 0.4% or 0.8% Mn produced by semi-solid casting process were studied. The semi-solid slurry of the alloys was prepared by ultrasonic vibration (USV) process. With USV process, the average grain size of primary Si in the alloys could be refined to 21~24μm, whether with or without P modification. The P addition has no further refinement effect on the primary Si in the case of the combined use of USV with P addition. Without USV, the alloys contain a large amount of long needle-like β-Al5(Fe,Mn)Si phase and plate-like δ-Al4(Fe,Mn)Si2 phase. Besides, the alloy with 0.8% Mn contains a small amount of coarse dendritic α-Al15(Fe,Mn)3Si2 phase. With USV treatment and semi-solid casting process, the Fe-containing compounds in the alloys are refined and exist mainly as δ-Al4(Fe,Mn)Si2 particles with average grain size of about 18μm, and only a small amount of β-Al5(Fe,Mn)Si phase is remained. With USV treatment and without P modification, the ultimate tensile strengths (UTS) of the alloys containing 0.4% and 0.8%Mn produced by semi-solid process are 260MPa and 270MPa respectively at room temperature, and the UTS are 127MPa and 132MPa at 350°C.

Abstract: The influence of Nd on structure and properties of hypereutectic Al-Si alloys (Al-17.5%Si, Al-25%Si) was investigated in this paper. For Al-17.5%Si alloy, there is no obvious variation in morphology of primary Si before and after Nd modification, but the average size of primary Si is decreased from 34.73µm to 23.39µm after 0.3%Nd modification. Compared with initial sample, the tensile strength and yield strength of 0.3%Nd-modified sample are increased by 11.6% and 1.5%, and wear resistance of Al-17.5%Si alloy is enhanced to a factor of 2.1 after 0.3%Nd modification. However, for Al-25%Si alloy, the tensile strength and yield strength of 0.3%Nd-modified sample are respectively improved by 22.1% and 9.5% as compared to initial sample. Meanwhile, wear resistance of modified sample is improved to a factor of 3 relative to initial sample. The property improvement of two alloys can be attributed to the change in morphology and size of primary Si after Nd modification.

Abstract: This paper preliminarily explored and proved the feasibility of fabricating semisolid thixoforming billets for a hypereutectic Al-Si alloy (AlSi29Fe3) by severe plastic deformation (SPD) and semisolid remelting. In this paper, friction stir processing (FSP) was used to refine the coarse primary silicon particles and needle-shaped iron-rich phase of the hypereutectic Al-Si alloy. The results show that the semisolid thixoforming billets obtained by the above route contain fine spherical Al grains with mean size of 34m, and second-phase particles (both primary silicon and iron-rich intermetallic) of less than 10m. The microstructure is ideal non-dendritic semisolid structure. Therefore, SPD and remelting is a promising technology for the fabrication of semisolid thixoforming billets of the hypereutectic Al-Si alloy.

Abstract: Mg₂Si reinforced hypereutectic Al-Si in-situ composite was prepared and the effects of the isothermal holding temperature and time on Mg₂Si in the composite were researched. The results showed that there were the important effects of holding temperature and time in the solid-liquid phase region of the Al-Si alloy on the size and morphology of Mg₂Si. The size and morphology of Mg₂Si became smaller and round with the rising of the holding temperature and prolonging of the holding time. The suitable technology in the test was obtained, in which when being held at 615°C for 300s, the size of Mg₂Si decreased to 20.54μm and the shape factor of Mg₂Si reached about 0.67.

Abstract: In the present work, the Al-21Si-0.8Mg-1.5Cu-0.5Mn alloys composite modified by P+RE was prepared by metal mold casting. The tribological properties against steel under lubrication conditions were experimentaled. The wear morphology characteristics and subsurface microstructure was characterized by means of optical microscope and scanning electron microscope. The effects of Si particle morphology, size, quantity and distribution on tribological properties were investigated. The wear mechanism based on lubricant abrasion was discussed. The results show that the wear mechanism of experimental alloy are mainly abrasire wear and fatigue spalling.