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To enhance the scuffing resistance of Al-Si alloy cylinder liners, mechanical honing shaping was employed. Comparisons were made with untreated and chemically etched Al-Si alloy cylinder liners. The scuffing resistance properties were evaluated using a starved lubrication test method. CrN piston rings (coated via PVD) and Chrom-Keramik-Schicht (CKS) piston rings were used in the tests against the cylinder liners. A stress contact model was established based on the state of silicon particles to analyse the scuffing resistance mechanism. The results indicated that the PVD piston ring exhibited superior scuffing resistance compared to the CKS piston ring. This improvement is attributed to the numerous small holes on the surface of the PVD piston ring, which effectively store oil. The mechanically honed Al-Si alloy cylinder liner demonstrated the best scuffing resistance properties. When paired with the PVD piston ring, the friction coefficient of the mechanically honed Al-Si alloy cylinder liner decreased by 17%, and the scuffing time increased fivefold. Finite element analysis revealed that the silicon particles protruding on the surface of the mechanically honed Al-Si alloy cylinder liner had a rounded shape, resulting in lower stress during friction. [ABSTRACT FROM AUTHOR]

The influence of ageing and ageing time on the mechanical properties, such as tensile strength and wear behaviour, of Al18Si3.6Cu0.34Ce alloy have been discussed. The As-cast alloy was subjected to T6 heat treatment (solutionization at 510° for 1 hr and ageing at-210°C) for different ageing durations like 1 hr, 3 hr, 5 hr and 7 hr, the morphology of as-cast and age hardened samples is examined by SEM and optical images, the sharp edges of primary-silicon and α-Al matrix with a columnar grain structure of untreated alloy changed after ageing, they are rounded off, spheroidisation with uniform redistribution of Al2Cu blocks, Al2CeSi intermetallic precipitates are formed with improved grain boundaries, and it develops obstacles in larger scale to the flow of dislocation mechanism, so it strengthens the metal matrix. Compared to as-cast alloy, the mechanical properties are improved after ageing. For 5-hr aged samples, the yield strength (YS) elevated to 127.44 MPa (improved by 83%) with an elongation rate of 1.64% (41.4%) as compared to as-cast alloy, and the ultimate tensile strength of as-cast alloy (158.2 MPa) enhanced to 193.835 MPa and 168.7 MPa after 1 hr and 3 hr ageing, respectively. Ageing improves the flow stress, which is predominantly the effect of homogenisation. Considerable improvements in the wear resistance after age hardening were noticed; both VWR and COF both a linear relation, with applied load at constant speed. As-cast and 7-hr aged samples show poor wear resistance due to co-existence of incoherent phases (Al2Cu and Si) in the metal matrix, and alloy ageing for 1 hr, 3 hr and 5 hr improves the load bearing and shear strength. [ABSTRACT FROM AUTHOR]

Silicon has the advantages of high specific capacity (4200 mAh/g), low lithium potential and abundant reserves, and is considered to be one of the most suitable materials for replacing graphite negative electrode. However, the commercial silicon particle size is too large to be used directly as an electrode material, and the silicon material will undergo huge volume expansion during the lithium insertion process, resulting in the fragmentation of the active substance falling off from the fluid collector, resulting in a sharp decline in battery capacity. This defect seriously affects the commercial application of silicon-based anode materials. In this paper, a kind of silicon anode material with porous structure is designed for the defect of silicon anode material. The aluminum-silicon alloy prepared by atomization method presents a three-dimensional porous spherical structure after etching, and the abundant holes reserve space for the volume expansion during the process of lithium silicon embedding and improve the transmission rate of lithium ions. It was found that when the silicon content was 12%, the reversible specific capacity of the material was 1269 mAh/g at 4000 mA/g current density, and the capacity retention rate of 100 cycles relative to the fourth cycle was 59.5%. Compared with ball-ground silicon, the capacity retention rate is increased by 25.7%. Therefore, this paper provides a new idea for the design of porous silicon-based anode materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The corrosion mechanism evolution of four low silicon-cast aluminium alloys exposed to heat treatment at 200°C for 0–50 h was studied by means of immersion corrosion, intergranular corrosion and electrochemical test, SEM, EDS and EBSD analysis methods. The correlation of corrosion resistance with composition and the thermal exposure time was investigated. The results show that the corrosion mechanism of all aluminium alloys changed after thermal exposure at 200°C. Before thermal exposure, intergranular corrosion was the main corrosion, and after 200°C thermal exposure, serious pitting corrosion and spalling corrosion occurred in the local area. The contents of Si and Mg in the grain boundary increased obviously. The contents of elements in the poor zone of the grain boundary increased, and the electrical potential difference between the grain and the grain boundary reduced. The intergranular corrosion sensitivity of the alloy was reduced. But the degree of pitting gradually becomes serious. The electrochemical test of the aluminium alloy with 3.5 wt% Si showed that its corrosion potential increased with the increase inthermal exposure time, and its corrosion current density increased with the increase inthermal exposure time. After the EBSD test, it was found that the large angle grain boundary decreased gradually and the proportion of large grain size increased with the increase in thermal exposure time to 50 h. [ABSTRACT FROM AUTHOR]

Additive manufacturing of Al-Si alloy thin-walled components with/without interlayer adding La2O3 powder were obtained by cold metal transfer (CMT). Based on the optimisation of the CMT additive manufacturing process, the influences of La2O3 powder on the microstructure and properties of parts were analysed by using OM, SEM and EBSD. The results showed that by adding La2O3, the effective length and layer height of the component was increased due to the increase of the surface tension. Nucleation particles were increased by adding the La2O3, which resulted in that the α-Al and Al-Si eutectic were refined compared with that of no adding La2O3. By adding La2O3, the tensile properties of the part were improved. The refinement microstructure was the main reason for the improvement of mechanical behaviour. [ABSTRACT FROM AUTHOR]

This paper presents the study of the microstructure, wear properties of spray-deposited and hot compressed Al-35Si and Al-45Si alloys. The microstructure analysis and wear mechanisms of spray formed and as cast alloys were studied by using optical and scanning electron microscope (SEM). The microstructure of the spray-formed alloys showed fine particulate of primary Si and eutectic phases distributed uniformly in the equiaxed Al- matrix. Microstructural refinement was further increased in the hot-compressed alloys. Hardness, dry friction and wear tests were performed on spray formed alloys and compared with as cast alloys. Friction coefficient (COF) and wear rate of the alloys were measured under different applied loads (10–50 N) and sliding velocities of 1 and 1.5 m/s at constant sliding distance of 5000 m. The results indicated that the hardness and wear resistance of spray formed and hot-pressed alloys were considerably high over that of the as cast alloys. The improvements in hardness and wear resistance of spray-formed alloys were mainly attributed to morphology, size and distribution of Si particles induced during spray deposition process. Analysis of worn surfaces by SEM showed dominant wear mechanism of spray-formed alloy was mainly abrasive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

The effects of Mg on microstructure, defects and properties of Al–Si alloy deposited by Wire and Arc-based Additive Manufacturing (WAAM) were investigated. The WAAM alloys were characterised by the metallographic microscope, X-ray diffraction, scanning electron microscope, computed tomography and electronic universal testing machine. The results show that the secondary dendrite arm spacing (SDAS) and hydrogen content of as-deposited WAAM alloy increase, and the tendency of pore formation increases with an increase in Mg content. The impurity Fe in the WAAM alloy with low Mg content is mainly in β-Fe phase, while with high Mg content is mainly in the π-Fe phase. After solution treating and ageing treatment (T6 heat-treat), the microstructure of WAAM alloy tends to be uniform. With the increase of Mg content, the size of eutectic silicon particles increases gradually. Furthermore, the UTS and YS of the alloys increased, and the elongation decreased. [ABSTRACT FROM AUTHOR]

The Al-Si-Cu-Mg-Ni alloy is a commonly used piston alloy. In this work, different amounts of phosphorus modifier and Al-2P (Al-2%P) master alloy modifier were added to the original alloy. The ultrasonic melt treatment method was also applied to improved the microstructure of near-eutectic multi-cast Al–Si alloys. Investigation was performed by means of optical microscopy and scanning electron microscopy. The results show that the effect of Al-2P master alloy modifier is more stable. However, the phosphorus modifier requires a higher amount of addition to achieve a refinement effect similar to that of the Al-2P modifier. The external ultrasonic field mainly acts on the AlP particle. The heterogeneous nucleation of the primary Si phase and the AlP clusters formed by the phosphorus modifier are more aggregated than the fine-dispersed AlP particles formed by the Al-2P master alloy modifier in the melt. Hence the ultrasonic melt treatment is more effective for the phosphorus modification. [ABSTRACT FROM AUTHOR]

In this study, Al-Si/fly ash spherical high temperature shaped composite phase change material (heat storage ball) was made, and an experimental device for heat storage and release characteristics of the heat storage ball was designed and built. The experiment verified that the accuracy of the device met the requirements. The surface and center temperature of four heat storage spheres with different heating/cooling rates and different pressing processes were measured and their heat storage and release characteristics were analyzed. The results show that the heating/cooling rate is higher, the heat storage/release rate is higher, the temperature difference between the surface layer and the center of the heat storage sphere is greater, the heat transfer resistance is greater, and the heat storage/release efficiency is lower. The heating/cooling rate and the diameter of the regenerative ball had little influence on the temperature at the melting/solidification starting point, but had great influence on the temperature at the melting/solidification ending point of the regenerative ball. The phase transition temperature range of Al-Si alloy was expanded, the heating rate was higher, the melting termination point temperature was higher. Higher grade heat energy was needed for heating and heat storage, it increased the requirement of heat source. The end temperature of solidification of cooling rate 6°C/min and 9°C/min was lower than 500°C, it exceeded the lower limit of high-temperature heat storage/exothermic temperature, and the utilization of high-temperature heat energy could not be realized. For high-temperature heat storage/release, the 15 diameter heat storage ball was prepared by the process (1), phase change latent heat was high and heat storage was ample. When the heating/cooling rate was 3°C/min, the phase change temperature range of Al-Si alloy was relatively reasonable, the heat storage phase change temperature was 567.0 ~ 599.9°C, and the exothermic phase change temperature was 542.4 ~ 504.7°C, it met the requirements of high-temperature heat storage/release. [ABSTRACT FROM AUTHOR]

Nowadays, Squeeze casting is considered as a convenient process for developing quality piston components. In this paper, casting methods such as squeeze casting and die casting techniques are used for compare the tensile behavior of Al-Si piston in the view of casted and heat-treated aspects. K-Nearest Neighbour (KNN) algorithm is used for predicting the tensile fracture of the squeeze casted Al-Si alloy. The proposed method is implemented in the MATLAB platform, and the tensile fracture in casting is compared with the experimental and predicted value. The scanning electron microscope analyzes the microstructural property and fractures analysis of the material. The maximum ultimate tensile strength of the casted and heat-treated specimen is 184 MPa and 297 MPa. The results indicate the proposed approach is an efficient method than the implemented Artificial neural network for predicting the tensile fracture in Aluminium-Silicon alloy materials. [ABSTRACT FROM AUTHOR]

The microstructure evolution and property change of four kinds of low silicon cast aluminum alloy exposed to heat for 0–50 h at 200°C were studied by means of Brinell hardness test, tensile property test, friction and wear property test and XRD analysis. The results show that with increasing thermal exposure time, the tensile strength of each group of samples decreased and the amount of wear increased. The tensile strength of samples with more Si content decreased slowly. When the time increased to 50 h, the increase of wear loss was the largest. The hardness of samples after thermal exposure increases compared with that before thermal exposure. The residual stress of (311) diffraction crystal surface of AlSi3.5Mg0.66 under different thermal exposure time was measured. The type of residual stress changed from residual tensile stress to residual compressive stress after thermal exposure. There is an abnormal phenomenon that the hardness of the sample increased and the amount of wear increased, and it is evident that the distribution of residual stress was inhomogeneous after thermal exposure. It is found that with increasing thermal exposure time to 50 h, the average lattice distortion ε of the low-index crystal plane and the high-index crystal plane in the aluminum alloys gradually increased. [ABSTRACT FROM AUTHOR]

The solidification behaviour of Al-Si based alloys with controlled additions of Eu (up to 200 ppm) and P (up to 10 ppm) was investigated using thermal analysis in a conventional die casting condition. The results indicate that P may be removed or involved into the formation of EuP phase. Furthermore, the formation of EuP phase appears to have a beneficial effect on the nucleation of Si and thereby the refinement of eutectic grains. A simultaneous modification of the eutectic Si and refinement of the eutectic grains was achieved by a combined addition of Eu and P, which is believed to be of extremely importance to optimize the number, size and size distribution of casting defects. The observation and analysis of pores using computed tomography strongly supports this argument. The obtained results in the present investigation can, therefore, give some novel insights in controlling the solidification microstructure of Al-Si based alloys. [ABSTRACT FROM AUTHOR]

A direct chill (DC) cast Al-15% Si alloy was processed by hot rolling with a single pass at a temperature of 520°C with a thickness reduction of 80%. Scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM) were used to investigate the evolution of the sample's microstructure. After hot rolling, silicon particles homogeneously distributed in the Al matrix with fine equiaxed grains of average size ∼ 0.95 μm. High-angle boundaries (HABs) (about ∼75.8% in percentage) dominate in the Al matrix structure. There is evidence for Si-particle-stimulated continuous dynamic recrystallization (CDRX) during hot rolling. [ABSTRACT FROM AUTHOR]

Newtonian and Fourier analysis techniques were used to calculate the solid fraction and latent heat during the solidification of Al-8Si alloy and the subsequent results were used to study the effect of Sr modification on thermal diffusivity of the solidifying melt. The results indicate that the thermal diffusivity increased significantly with increase in Sr content. The increase in the thermal diffusivity was attributed to the increase in the electronic conduction of the modified alloy due to the decreased activity of the bifilm. The results also indicate that the latent heat evolved during solidification increased with increase in Sr concentration and was associated with the increase in the solidification range that occurred during the modification process. [ABSTRACT FROM AUTHOR]

The effect of individual and combined minor element additions (Sr, Sb, Mn, Cr and Al-5Ti-1B grain refiner) on microstructure and mechanical performance of a secondary cast aluminium piston alloy, with 1 wt-% Fe was investigated. It was observed that addition of Cr of up to 1% was better than a 0.53%Mn addition in improving tensile strength, impact energy and percent elongation of the alloy. The high mechanical performance recorded with addition of 1%Cr alloy was attributed to the significant reduction in porosity levels compared to all other minor element additions. It also resulted in a microstructure with fine compact intermetallic compounds. Other element additions also resulted in improved mechanical properties with 0.53%Mn performing better than 0.3%Mn + 0.2%Cr. Marginal improvements in mechanical performance were recorded with addition of 0.02%Sr (or 0.05%) and 0.02%Sb individually or in combination with 0.53%Mn. This was attributed to general increase in porosity and volume fraction of intermetallics. [ABSTRACT FROM AUTHOR]

The occurrence of scuffing is widely observed on tribological components made of Al-Si alloys. The object of this study is to investigate the scuffing behavior of Al-Si alloy modified by fine particle bombarding (FPB) and powder impact plating (PIP) hybrid surface treatment. FPB treatment, PIP treatment, and hybrid treatment consisting of FPB and PIP were conducted on Al-Si alloy samples. The surface morphology, microstructure, and hardness of the samples were examined. Block-on-ring tests were performed to investigate the scuffing resistance of the samples. The test results show that the scuffing resistance of Al-Si alloy depends on the surface hardness and friction coefficient. Scuffing resistance is improved by FPB treatment, which increases the surface hardness by nanocrystallization and reduces the friction coefficient by decreasing the surface roughness and producing a microdimpled surface. PIP treatment reduces the friction coefficient by generating an Sn coating on the surface of the sample, thereby improving the scuffing resistance. After FPB and PIP hybrid surface treatment, the surface hardness is increased and the friction coefficient is further reduced. Therefore, the sample modified by hybrid surface treatment exhibits the highest scuffing resistance. [ABSTRACT FROM AUTHOR]

The addition of CrB2and Sr into Al-10Si-0.3 Mg (wt.%)-based alloys not only modify the eutectic Si, but also refine the eutectic grains. CrB2particles were found to nucleate the eutectic grains, despite the AlP particles being partly removed or depleted by the interaction between Sr and AlP. Furthermore, P level was found to be one of the dominant factors that affect the nucleation of eutectic grains. CrB2addition with a low P level results in a refined eutectic grain size, despite less AlP particles being present to nucleate the eutectic grains. Porosity was found to be mainly located at the boundaries of eutectic grains, highlighting the importance of the refinement of eutectic grains to reduce the size and optimise the distribution of porosity. This investigation demonstrates a novel approach to refine eutectic grains and modify eutectic Si simultaneously into Al-10Si-0.3 Mg (wt.%)-based alloys, and thereby suggests possible industrial applications. [ABSTRACT FROM AUTHOR]

Electromagnetic continuous casting (EMCC) exhibits great potential for silicon purification by Al–Si method. Distribution of Al in Al–Si alloys with different aluminium contents during EMCC was investigated. The macrostructure of the Al–Si alloy ingots reveals that the content of primary silicon plates in hypereutectic alloys decreases from the bottom to the top of the ingots, and no obvious primary silicon plate exists in eutectic alloy. The fitting results of aluminium distribution in the alloys reveal two types of aluminium distribution patterns in hypereutectic Al–Si alloys: Scheil model for high temperature solidification and initial transient model for low temperature one. An apparent segregation coefficient of Al is proposed to characterise the solidification process, which is ∼0.83 in the hypereutectic alloys. [ABSTRACT FROM PUBLISHER]

Layered composite structures can be generated in metallic sheets by roll bonding of dissimilar metals/alloys. In this investigation, heat treatable (Al(Cu)) and non-heat treatable (Al(Si)) aluminium alloys are roll bonded in sheet form. Large hardness differences between layers poses significant bonding challenges in the form of multiple necking within the hard Al(Cu) layers. For successful processing, it is vital to choose the candidate materials in a state of marginal hardness differences during rolling, but being capable of altering properties through subsequent heat treatments. Atomic diffusion takes place during heat treatment of the composite sheet and results in gradual hardness variation across sheet thickness. The Al(Cu) layers contribute to strength, whereas the Al(Si) layers provide protection from corrosion/wear-related degradation in the newly developed hybrid sheet. The overall mechanical properties of the heat-treated composite fall between the base alloys. The bonding interfaces are noted as the potential spots for initiating failure. [ABSTRACT FROM PUBLISHER]

Porosity formation in a Sr modified A356 alloy was investigated using microfocus X-ray imaging and directional solidification technology. In situ experimental results indicate that Sr addition enhances the effectiveness of oxide inclusions in the liquid aluminium alloy as pore nucleation sites and thus leads to a remarkable rise in the nucleation temperature. As pores are nucleated in high temperature region and far away from the solidification front, they can grow at a high growth rate for a relatively long time, and thus, significant increases in the volume fraction of porosity and particularly the number density of large pores are seen in the Sr modified alloy. The growth rate of pores decreases with the reduction in local liquid temperature, and it fluctuates violently during directional solidification. Addition of Sr weakens this fluctuation and decreases the average growth rate of pores. Addition of Sr has a considerable influence on the size distribution of pores. [ABSTRACT FROM AUTHOR]

This study investigated the effect of applied load, sliding distance, and weight percentage of reinforcement on the abrasive wear characteristics of in situ synthesised Al-12Si/TiC composites using a pin-on-disk machine. The strength, hardness, and percentage porosity were also investigated. Scanning electron microscopy (SEM) was utilized to study the microstructure and wear surface behavior of the experimental materials. The results revealed that the strength and hardness increased with increasing weight percentage of reinforcement. However, the percentage porosity was relatively high in the higher weight percentage of reinforcement. The weight loss and coefficient of friction increased with increasing applied load and sliding distance. In contrast, the weight loss and coefficient of friction decreased when the weight percentage of TiC increased. Wear debris in the form of fine black powder and small grooves were noticed in the SEM micrograph of the abraded surfaces of all tested materials. [ABSTRACT FROM PUBLISHER]

A series of Al-5 wt-%Si alloys with or without 200 ppm Y addition have been produced using conventional casting and melt spinning respectively. The effects of Y addition and cooling rates on the refinement of eutectic Si have been investigated using thermal analysis, differential scanning calorimetry and multiscale microstructure characterisation techniques. In the case of conventional casting, the addition of up to 200 ppm Y was found to cause no modification effect. The eutectic Si presented a plate-like structure rather than a fibrous morphology. No significant Si twinning was observed. In the case of melt spinning, a higher cooling rate caused a much finer eutectic Si and Si twinning. The addition of 200 ppm Y promoted heavier multiply Si twinning. After a continuous cooling from 873 to 673 K, an Al2SiY phase was observed beside or within the Si particle. The refinement mechanism was also discussed. [ABSTRACT FROM AUTHOR]

The nucleation and growth of Si has been investigated by TEM in a series of high purity melt spun Al–5Si (wt%)-based alloys with a trace addition of Fe and Sr. In the as-melt-spun condition, some twinned Si particles were found to form directly from the liquid along the grain boundary. The addition of Sr into Al–5Si-based alloys promotes the twinning of Si particles on the grain boundary and the formation of Si precipitates in the α-Al matrix. The majority of plate-shaped and truncated pyramid-shaped Si precipitates were also found to nucleate and grow along {111}α-Al planes from supersaturated solid solution in the α-Al matrix. In contrast, controlled slow cooling decreased the amount of Si precipitates, while the size of the Si precipitates increased. The orientation relationship between these Si precipitates and the α-Al matrix still remained cube to cube. The β-Al5FeSi intermetallic was also observed, depending on subsequent controlled cooling. [ABSTRACT FROM AUTHOR]

An experiment on the directional solidification of Al-7Si alloys under the influence of a pulsed magnetic field (PMF) is performed. Maximal peak value of PMF intensity up to 0.226 T between two iron cores was generated when a capacitor bank of 120 µF capacitance with initial voltage of 1000 V was triggered to a pair of solenoids. The PMF decreases the temperature gradient ahead of the liquidus front and increases the width of the mushy zone. The convection of symmetrical vortices seems to charge the intersectional growth of primary dendrite stems and the decrease of dendrite arms spacing under a PMF with higher magnetic intensities. Using Darcy's permeability law and Lehmann's model, the order of magnitude of the interdendritic liquid flow velocities with the application of PMF is evaluated. A strong damped effect of the mushy zone in the bulk flow of the melt is revealed. [ABSTRACT FROM PUBLISHER]

Dimpled textures were prepared by using a pulse solid laser on the surface of Al-Si alloy. The combination of laser surface texturing (LST) and MoS2 solid lubricant as well as their tribological properties were investigated in this article. The obtained friction and wear data were critically analyzed to investigate how the parameters of texture influence the tribological performance of Al-Si alloy. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms are discussed. The results show that the combination of LST and solid lubricant improves the tribological characteristics of Al-Si alloy. The friction coefficient of Al-Si alloy: steel friction pairs can be reduced to 0.15 under dry friction. The lubricationmechanism is attributed to a synergetic effect of providing solid lubricant and traps wear debris in the dimples. It was found that the optimum density of structure was 37% for excellent tribological properties. [ABSTRACT FROM AUTHOR]