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The semi-solid slurry preparation process, microstructure, and mechanical properties of truck coarse filter bracket were studied in this paper. The semi-solid aluminum alloy slurry with high solid fraction was prepared by the Slurry Enthalpy Equilibrium Device (SEED) method, and the optimum slurry preparation parameters were determined through the observation and analysis of the slurry microstructure as follows: pouring temperature 700 °C, rotation speed 180 r/min, and crucible temperature 400 °C. The average grain size and shape factor of the slurry prepared under these conditions are 50.448 μm and 0.799. Die casting trial production which used the best process parameters of slurry preparation and die casting was carried out. The results show that the die casting parts are completely filled with no obvious surface defects. It can be seen from the cutting experiment and X-ray non-destructive test that the internal structure is dense and uniform, and there are no obvious casting defects that were observed such as cracks and holes. The semi-solid die castings were strengthened by T6 heat treatment. The experimental results showed that the optimal heat treatment parameters were a solution temperature of 470 °C and time of 4 h, aging temperature of 175 °C and time of 12 h. Under these conditions, the microstructure morphology was improved significantly. The tensile strength and yield strength reached 342.1 MPa and 309.1 MPa, respectively, which were 38.9% and 95.3% higher than the semi-solid state, and the elongation was 4.5%. [ABSTRACT FROM AUTHOR]

We employed a melt ultrasonic treatment near the liquidus to prepare a high-thermal-conductivity Al-4Si-2Ni-0.8Fe-0.4Mg alloy. The influences of various ultrasonic powers on its microstructure, mechanical properties, and thermal conductivity were investigated. It is shown that near-liquidus ultrasonication significantly refines the alloy grains and eutectic structure, synergistically improving the alloy's mechanical properties and thermal conductivity. Specifically, the grain size decreased by 84.5% from 941.4 to 186.2 µm. Increasing the ultrasonic power improved the thermal conductivity of the alloy slightly and significantly enhanced its mechanical properties. At an ultrasonic power of 2 100 W, the tensile strength, yield strength, elongation rate, and thermal conductivity were 216 MPa, 142 MPa, 6.3%, and 169 W/(m·k), respectively. [ABSTRACT FROM AUTHOR]

The evaluation of mold properties is crucial in the foundry industry to ensure efficient and high-quality casting production. This study focuses on the assessment of mold properties using silica sand, copper slag, and their mixture as molding materials in the sodium silicate, CO2 (carbon dioxide) chemical binder process. The properties investigated include mold hardness, permeability, and compressive strength. The aim is to evaluate their suitability and performance in comparison with traditional molding materials. The results indicate that a mixture of 6% sodium silicate and 15 sec of CO2 gas passing is highly effective in achieving optimum mold properties for both slag and sand molds. These properties remained stable even after prolonged exposure to different weathering conditions, highlighting the durability of the molds. Furthermore, the study revealed that the combination of sand and slag yields mold properties that lie between those of the pure ingredients. Specifically, a mixture comprising 80% sand and 20% slag exhibited the most desirable properties. Additionally, investigations were conducted using a 20% sand and 80% slag mixture, which demonstrated improvements in mold properties. In terms of material substitution, the evaluation of mold properties using the CO2 process showed that copper slag displayed similar characteristics to sand. This finding suggests that copper slag can serve as a suitable alternative to partially or fully replace silica sand in mold-making applications. [ABSTRACT FROM AUTHOR]

The present work investigated the effect of flat, concave, and convex mold contours on heat transfer during the solidification of an aluminum AlSi11Cu3Fe (ADC-12) alloy. Experiments were designed with copper/steel cylindrical and flat molds to study the effect of convex and flat casting/mold interface on heat transfer. To examine the effect of a concave and flat interfaces, an experimental setup consisting of a cylindrical and square bar chill was fabricated. Casting/mold (chill) interfacial heat flux was estimated by solving an inverse heat conduction problem (IHCP). The temperatures measured at locations inside the mold/chill were used as input to the inverse solver. It was observed that the flat contour yielded higher heat flux than a convex contour for both copper and steel molds. Although the volume to surface area (V/A) ratio for castings solidified against a flat and convex interface are the same, the larger mold volume associated with the flat interface yielded higher heat flux transients. Experiments involving chills suggested that the flat interface resulted in higher heat transfer when the (V/A) ratio for the chill was the same. To study and compare the combined effect of mold material and contour on heat transfer during casting solidification, the molds must have the same volumetric thermal effusivity per unit surface area available for heat transfer. [ABSTRACT FROM AUTHOR]

Near-eutectic Al–Si alloys attracted significant interest in automotive, aerospace, and other industries owing to their superior strength and high-temperature resistance. However, the alloy's narrow solid–liquid temperature range presents challenges in semi-solid processing. In this study, an Enclosed Cooling Slope Channel was used to prepare near-eutectic Al–12Si–4Cu–2Ni–0.8Mg–0.1Gd alloy semi-solid slurry. We investigated the impact of liquid squeeze casting (LSC) and rheo-squeeze casting (RSC) on the alloy's microstructure characteristics and properties of the alloy were explored. Findings indicate that the average size of primary α-Al decreases first and then increases with the rising pouring temperature. Through the RSC process, the ultimate tensile properties of the material are significantly improved, achieving optimal tensile properties at the pouring temperature of 605 °C, with ultimate tensile strength and elongation of 247 MPa and 2.66%, respectively. Compared with LSC samples, the ultimate tensile strength and elongation increased by 44.4% and 116.3%, respectively. This enhancement in properties is credited to the notable reduction in porosity and the spheroidization of primary α-Al. Regarding high-temperature performance, the alloy's tensile strength at a test temperature of 200 °C stands at 194.6 MPa. marking only a only 21.2% decrease from the room temperature result. The precipitation of the thermally stable phase and the solid solution effect of Gd elements effectively hindered the reduction of high-temperature tensile properties. [ABSTRACT FROM AUTHOR]

In this study, the friction surfacing of Al–16Si alloy on AA1050 substrate was investigated using experimental and smoothed-particle hydrodynamics simulation methods. The effect of Al–16Si rod rotational speed on microstructure, surface roughness, mechanical properties, and wear resistance of coatings was examined. Both experiment and simulation findings show that by enhancing the rotational speed from 600 to 1000 rpm while reducing the effective width and thickness of the deposited layer, the deposited layer's efficiency decreases from 41 to 14%. By increasing the rotational speed from 600 to 1000 rpm, the interface roughness and surface roughness decreases to 78 and 80%, respectively. According to experiment and simulation results, plastic strain's influence on the grain size is dominant at a high rotational speed (1000 rpm), and by decreasing the rotational speed down to 600 rpm, the effect of temperature is dominant. In addition, the distribution of CuAl2 and silicon particles become more uniform with a decrease in the rotational speed from 1000 to 600 rpm, and the average size of these particles decreases to 0.62 and 4.35 μm, respectively. Compared to the pure aluminum substrate, surfacing with a rotational speed of 600 rpm increases hardness, shear strength, and wear resistance by 224%, 265%, and 60%, respectively. [ABSTRACT FROM AUTHOR]

The effects of Al-5Ti-1B and Sr on the microstructure and properties of ZL101 alloy were studied, and the degree of eutectic Si modification was evaluated by solidification behavior. The results show that Al-5Ti-1B has a great effect on the refinement of primary α-Al dendrites, Sr has a great effect on the modification of eutectic Si, Al-5Ti-1B and Sr have a significant effect on the refinement of α-Al, and most of the eutectic Si is transformed from coarse lamellar to fine fibrous, but an incompletely modified region appears. Thermal analysis shows that the degree of undercooling in the primary α-Al and the nucleation rate is increased by the combined addition of Al-5Ti-1B and Sr, the effect of grain refinement is good, and the growth temperature of eutectic Si in the precipitation stage increases, and the metamorphic effect decreases slightly. More importantly, compared with the unmodified alloy, the alloy with Al-5Ti-1B and Sr addition combined increased the hardness by 9.8% and the electrical conductivity by 8.9%. The influence mechanism of the interaction between Al-5Ti-1B and Sr on the microstructure and properties of the alloy is discussed. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of adding Mn to a 0.5%Cu-added A356 alloy on the interfacial layer formed between the alloy and cast iron in compound casting. The results showed that the interfacial compounds layer thickness and the types of phases constituting the layer were significantly influenced by the addition of Mn. Microstructural analysis of the interface revealed an increase in interlayer thickness with the addition of 0.3%Mn. Moreover, the almost absence of Al4.5FeSi phase in the interfacial layer, which is typically observed close to aluminum region, was noted when Mn was added. Instead, the formation of Al(Fe,Mn)Si phase containing Mn was observed with the addition of 0.3%Mn. The Mn-rich phase was identified as cubic-Al(Fe,Mn)Si phase through TEM analysis. Additionally, comparing the nanoindentation hardness of the interfacial compounds layer of the Mn-added alloy with that of the base alloy (0.5%Cu-added A356) showed that the hardness near the aluminum region was relatively higher in the Mn-added alloy. [ABSTRACT FROM AUTHOR]

Aluminum alloys with 40 to 50 wt.% silicon content are potential material candidates for the manufacturing of satellite components. These materials have excellent thermal and mechanical stabilities, but machining complex components from these alloys is facing many challenges. The present study was performed on an aluminum-high silicon alloy (50–50 wt.%) with the main aim of investigating the evolution of the microstructure with particular attention to surface and subsurface damage as a result of Electrical Discharge Machining (EDM). For this purpose, the microstructure was characterized by optical and Scanning Electron Microscopes (SEM) as well as Energy Dispersive Spectroscopy (EDS) of the machined samples. The results show the existence of melted and re-solidified zone with much finer silicon particles located in a zone on the top of the machined surface where cracks were also observed. Moreover, SEM examinations showed that the cracking damage concern the primary silicon particles. Possible mechanisms, such as the thermal shock produced by rapid cooling rate of the primary silicon particles and the presence of porosities, formed during the manufacturing process, are discussed. [ABSTRACT FROM AUTHOR]

Permanent mold casting produces the second most aluminum cast parts among all casting processes. In this process, mold coating changes the heat transferred from the molten metal to the mold by acting as an insulating layer. Moreover, the coating thickness is a significant variable regarding the coating's thermal resistance, which strongly influences the microstructure of cast parts and the thermal shock on expensive molds. However, in casting production, coating peeling-off and repeated recoating result in an inhomogeneous coating thickness distribution. Due to the high working temperatures of the molds, no efficient online coating thickness measurements exist. We propose an indirect evaluation method based on the as-cast surface corresponding to the coating area. Our experiments analyzed as-cast and coating surfaces at nine different coating thicknesses. The results show a close correlation between the as-cast surface roughness parameter of arithmetical mean height Sa and the coating thickness. Based on this correlation, we can derive the coating thickness from the corresponding as-cast surface analysis. Furthermore, the coating peel-off area and other casting surface defects are easily recognized in these surfaces. In our next work plan, an affordable optical camera and proper light conditions will be tested by taking photos of as-cast surfaces, and an algorithm for the real-time automatic evaluation will be developed. [ABSTRACT FROM AUTHOR]

The effects of mixing temperature, i.e., the temperatures of two precursor melts (pure Al and Al-12Si), on the temperature and solute fields of resultant mixture, the nucleation and growth, and the size and morphology of primary grains during controlled diffusion solidification (CDS) of Al-8Si alloy were investigated by using simulation and calculation. The results indicate that a lower mixing temperature is helpful for achieving more supercooled microscale Al-rich pockets in the mixture, and increasing the width and supercooling degree of supercooling zone in the Al-rich pockets, and thus, the nucleation rate. The nuclei grow up in nondendritic mode, resulting in spheroidal, at least, nondendritic grains. In a successful CDS, the superheat degrees of the two precursor melts should be limited within several degrees, and it is not necessary to extra stipulate the superheat degree of target alloy melt (Al-8Si) when the requirement about Gibbs energies of the three melts is matched. Subsequent observation on casting microstructures shows that the employed simulation and calculation processes are reasonable and the achieved results are reliable. [ABSTRACT FROM AUTHOR]

The wear behaviour of the Al-7Si alloy was investigated in this study under various in situ TiB2 reinforcements (3, 5, and 7 wt%). These composites were made by reacting molten Al-7Si alloy with a combination of KBF4 and K2TiF6 at an 800 °C reaction temperature. Stir casting was used to evenly distribute TiB2 reinforcing particles in the Al-7Si alloy. The microstructure, worn surface, and phases of both matrix and composites were described using an optical microscope (OM), scanning electron microscopy (SEM), and EDS, respectively. The findings reveal the presence of a dendrite Al phase and a needle shape of eutectic Si phase in matrix alloys. The microstructure of the composites reveals homogeneous dispersion of TiB2 particles, grain refined Al, and eutectic Si phase in a short-rod shape. With an increase in TiB2 concentration, there was significant refinement in Al and a reduction in interspaced between eutectic silicon. The microhardness of base and composites containing various amounts of TiB2 was investigated. It was observed that the hardness of composites increases as the weight % of TiB2 increases when compared to matrix alloy. When compared to matrix alloy, the Al-7Si -7TiB2 composite had a nearly 45% higher hardness. Dry sliding at loads of 10, 20, 30, and 40 N with sliding velocities of 1, 2, and 3.0 m/s was used to investigate the wear characteristics of the base alloy and composites.. The wear rate was shown to decrease under all operating settings with greater TiB2 concentration, according to the findings. Abrasion and de-lamination were the dominating mechanisms at higher loads and sliding speeds. [ABSTRACT FROM AUTHOR]

In this study, pure Al and Al–12Si alloy were used as precursor alloy 1 and precursor alloy 2 respectively to prepare the target alloy of Al–8Si by controlled diffusion solidification with simultaneous mixing, and the effects of melt mass and pouring height on the casting microstructures were investigated via simulation and experiment. The results from the simulation indicates that as the melt mass increased, both temperature and concentration fields became more uniform, i.e., the mixing effect was improved due to the increased melt momentum. But when the melt mass exceeded 2 kg, an opposite effect was achieved because of the increased friction in the melt. With the increase in pouring height, the mixing effect was continuously enhanced due to the steadily increased momentum. However, more gas bubbles were entrapped within the melt. A better mixing effect means that more and finer pure Al pockets were formed and more uniformly distributed in the Al–12Si matrix melt. Thereby more α-Al grains nucleated to form a structure with finer and more spheroidal grains. Subsequent experiment results indirectly confirmed these simulation results. A casting with a grain size of 45.7 μm and shape factor of 1.36 was obtained at melt mass of 2 kg and pouring height of 600 mm. [ABSTRACT FROM AUTHOR]

Aluminum high pressure die casting (HPDC) technology has evolved in the past decades, enabling stronger and larger one-piece casting with significant part consolidation. It also offers a higher design freedom for more mass-efficient thin-walled body structures. For body structures that require excellent ductility and fracture toughness to be joined with steel sheet via self-piercing riveting (for instance, shock towers and hinge pillars, etc.), a costly T7 heat treatment comprising a solution heat treatment at elevated temperatures (450 °C-500 °C) followed by an over-ageing heat treatment is needed to optimize microstructure for meeting product requirement. To enable cost-efficient mass production of HPDC body structures, it is important to eliminate the expensive T7 heat treatment without sacrificing mechanical properties. Optimizing die cast alloy chemistry is a potential solution to improve fracture toughness and ductility of the HPDC components. The present study intends to tailor the Mg and Cu additions for a new Al-Si-Cr type die casting alloy (registered as A379 with The Aluminum Association, USA) to achieve the desired tensile properties without using T7 heat treatment. It was found that Cu addition should be avoided, as it is not effective in enhancing strength while degrades tensile ductility. Mg addition is very effective in improving strength and has minor impact on tensile ductility. The investigated Al-Si-Cr alloy with a nominal composition of Al-8.5wt.%Si-0.3wt.%Cr-0.2wt.%Fe shows comparable tensile properties with the T7 treated AlSi10MnMg alloy which is currently used for manufacturing shock towers and hinge pillars. [ABSTRACT FROM AUTHOR]

Additive manufacturing process is widely adopted for the development of near net shape components of complex geometries that are used in aerospace, automobiles, and medical industries. However, the variables like alloy types, process parameters, printing method, and printer types govern the defects formation, microstructure evolution, and mechanical properties of the component during service conditions. In this work, multiple machine learning models have been implemented to predict the densification of Al-50 Si alloy for the given input parameters. Three hundred and fifty samples have been printed by selective laser melting route for different power, scan speed, and hatch distance and their densification has been measured using Archimede's principle. Random forest, decision tree, and neural network-based algorithms have been used to predict the densification. The decision tree model exhibited R2 value of 93.16% and outperformed the random forest model. Neural network model has predicted the densification with a minimum mean square error of 1.1994×10−04 for 500 iterations. The random forest model is implemented to identify the importance of process parameters on the densification and it is also observed that the scan speed is the most significant and hatch distance is the least significant parameter. The three models are experimentally validated and neural network-based model is able to predict densification with accuracy. [ABSTRACT FROM AUTHOR]

The present study systematically evaluated the effects of a newly developed Al-1.25 wt%Ti-1 wt%V-1 wt%B grain refiner on the microstructure and tensile property of A356.2 alloy knuckle produced by the counter pressure casting process. The grain size of sampling region in the knuckle was reduced from 365.6 to 278.1 μm via using the Al–Ti–V–B grain refiner with half addition mass of a commercial Al-5 wt%Ti-1 wt%B grain refiner. A detailed analysis on the fracture surfaces indicates that grain refinement reduced the area fraction of shrinkage porosity from 0.14 to 0.10%. However, this slight reduction in shrinkage porosity fraction has minor impacts on tensile properties. After hot isostatic pressing (HIP) treatment, plastic elongation of the samples refined with the Al–Ti–V–B refiner has been improved from 10.7 to 12.6% owing to the elimination of porosity. However, plastic elongation of the samples refined with the Al–Ti–B refiner was not improved via HIP treatment. This phenomenon was attributed to a larger volume of granular alumina inclusions, which was not healed by hot isostatic pressing (HIP) treatment, in the samples refined with the Al–Ti–B master alloy. The present study indicates that in the Counter Pressure Casting (CPC) process of Al casting, grain refinement effect at this extent (from 365.6 to 278.1 μm) can hardly induce sensible impacts on microstructure and mechanical properties of the regions with well-designed progressive solidification, good feeding and relatively fast solidification rates. [ABSTRACT FROM AUTHOR]

Quality issues caused by casting defects are commonly complicated to solve, because the part-specific process parameters are not traced to the individual cast part. This problem can be mitigated by the traceability of each cast part with an identifier code. Therefore, a study of the influence of marked surface topography and post-treatments on code symbol quality is desirable for a well-designed traceability system. In this work, the code symbol quality of laser, dot peen, and electrolytic marking methods on three as-cast surfaces of Al–Si alloy, after sandblasting and heat treatment, is evaluated comparatively with a customized image processing software. The result shows that the laser marking method produces the highest performance for different as-cast surfaces; electrolytic marking provides acceptable results only on the smooth surfaces of high-pressure die casting; dot peen marking produces the codes of high symbol contrasts, which are similar to those of laser marking, especially for rough as-cast surfaces of sand casting. However, for all marking methods, the code qualities of all surface topographies decrease substantially after post-treatments. Considering that dot peen marking has satisfying performances as well as low equipment and maintenance costs, this method is more suitable for small- and medium-size foundries to start to trace each cast part in an economical manner. [ABSTRACT FROM AUTHOR]

The aim of this article was to investigate the influences of directions and magnitudes of static electrical field (E) on eutectic spacings (λ), Brinell hardness (HB) and ultimate tensile strength (σUTS), yield strength (YS) and % elongation (%El) in the Al–12.6 wt.% Si alloy. For this purpose, the Al–12.6 wt.% Si molten alloy was solidified with different directions and magnitudes of E. Directions of E were chosen to be parallel (E+) and antiparallel (E−) to the solid–liquid (S–L) growth direction, and the magnitudes of E were in the range of 14.1–17.9 kV cm–1. The E+ and E− provided an increment or decrement in the atomic mass flux of liquid Al atoms at S–L interface during the solidification. Thus, the value of λ increased as 100% and the values of HB and σUTS decreased as 6.3 and 6.2%, respectively, with increasing the E+. But the λ value decreased as 34% and the values of HB and σUTS are increased as 8.5 and 5.6%, respectively, with increasing E−. The dependence of λ, HB and σUTS on the E+ and E− was determined by regression analysis. [ABSTRACT FROM AUTHOR]

Solvent refining with Al-Si alloy is a promising purification method for the production of solar-grade silicon (SoG-Si) feedstock owing to the advantages of low production cost and high impurity removal efficiency. In this process, larger refined Si primary dendrites should be easily collected after acid leaching, which is favorable to recovery, thereby reducing the production cost. Hence, the growth behavior of the precipitated Si crystal must be investigated systematically. In the present work, the morphology evolution of solidified Al-Si alloys with a wide range of Si content (30 ~ 70 wt%) was analyzed. The typical plate-like Si primary dendrites grown following the twin plane re-entrance edge (TPRE) mechanism formed in all alloy compositions. As increasing the Si content from 30 wt% to 50 wt%, the Si primary dendrites underwent a coarsening process attributed to the preferred growth along with < 211 > and < 111 > directions, leading to an increase in the experimental recovery rate. However, the preferred growth along < 211 > direction was inhibited when the Si content is higher than 55 wt%. Moreover, the broken effect originating from grain collision and thermal stress on the Si primary dendrites was enhanced by further increasing the Si content, resulting in a decrease in the experimental recovery rate. Therefore, the optimum composition is determined as Al-50 ~ 55 wt% Si for solvent refining solution, based on the cost reduction consideration. [ABSTRACT FROM AUTHOR]

The effect of Eu (Europium) element on eutectic Si in Al–7Si alloys was studied by scanning electron microscopy (SEM), thermal analysis, electron backscattering diffraction (EBSD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to elucidate modification mechanism of Eu on eutectic Si. The results indicate that the addition of Eu changes the morphology of eutectic Si from coarse plate-like to fine fibrous. With the increase in Eu content, the number of eutectic cells gradually decreased and the size of eutectic cells increased. Meanwhile, the eutectic nucleation temperature (TN) and the minimum temperature (TMin) decreased, which is caused by the poisoning of AlP particles by Eu. The segregation of phosphorus was found at the center of coarse Al2Si2Eu particle, and the "phosphorus layer" was found at the boundary between the Al2Si2Eu particle and matrix. The length direction of plate-like eutectic Si was <110>, and its outer surface was {111} plane. Few parallel twins were observed in unmodified plate-like eutectic Si. However, the growth of Eu-modified fibrous eutectic Si was isotropous. Multiply twins were often observed in fibrous eutectic Si after modification. The adsorption of Eu was observed along the <112>Si growth direction of eutectic Si and at the intersection of two {111}Si twins, verifying the existence of the poisoning of the TPRE mechanism and IIT mechanism. [ABSTRACT FROM AUTHOR]

The effect of grain refiner on microstructural features, casting defects, formation of precipitates and eutectic Si particles, which influence the hardness and tensile properties of Al-Si alloys, is investigated in this study. The A-7Si alloy was prepared through melting and casting route with varying wt.% of Ti up to 0.2%. XRD, SEM and HRTEM analyses characterize the phases and aluminide (TiAl3 and Ti7Al5Si12) precipitates. The thermodynamic analysis, carried out by using FactSage software, confirms the presence of aluminides particle in the microstructure, which is formed at the liquid stage. The microstructure of as-cast Al-7Si alloy contains primary α-Al phase with dendritic morphology and eutectic phase having plate-like eutectic Si particle which is distributed at interdendritic regions. The morphology of primary α-Al grains is altered from dendrite network to fine equiaxed rosette type structure. Secondary dendrite arm spacing (SDAS) is reduced after adding grain refiner (Al-5Ti-1B) to the Al-7Si alloy. The eutectic Si is also refined to fine fibrous type particles. The shrinkage porosity and microcracks are also reduced after the addition of a grain refiner. The yield strength, ultimate tensile strength and elongation to fracture increase from 84, 117 MPa and 16% to 112 MPa, 148 MPa and 22%, respectively, after the addition of 0.1% Ti due to significant reduction in SDAS. Elongation decreases when the percentage of Ti increases more than 0.1%. The fracture mechanism of grain-refined alloy is changed from brittle to ductile fracture. [ABSTRACT FROM AUTHOR]

Al-Si based alloy matrix composites are now broadly utilized by the industrial sectors like automobile, structural, aerospace and more practical industrial applications due to its noncompetitive economy range, good mechanical properties and less density. In order to widen its applications, it is very significant to improve its mechanical and workability behavior. So, in this work, an effort has been taken to develop a ZnO microparticles (3, 4.5 & 6 %) reinforced with Al-Si-Mg (AA6061) alloy by stir casting route.Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (X-RD) were employed for characterization studies of the composites. Tensile and hardness of the composites are investigated, compared and analyzed its effects. Another novel finding of the work is determining the workability behavior of the prepared samples with aspect ratio of 1 by incremental compressive loading of 25 kN through cold upsetting technique. For all developed samples, true axial stress (σz), hoop stress (σө), hydrostatic stress (σm), effective stress (σeff), formability stress index (β) and stress ratio parameters [(σz/σeff), (σө/σeff), (σm/σeff)] were determined and the results are correlated with the axial strain (εz). The results clearly infers that increasing weight contributions of ZnO particles increase the mechanical properties, all the stresses and stress ratio parameters of the composites. [ABSTRACT FROM AUTHOR]

Aluminum foams with different silicon content have been produced by the Alporas method, where calcium and calcium carbonate are used as a thickening and foam agent, respectively. Performing quasi-static compression tests, mechanical behavior such as strain–stress diagram, deformation behavior, and energy absorption properties of the produced foams were investigated in this study. By adding silicon, calcium, and agitation of molten metal Si, SiO2, CaAl2Si2, CaAl2Si2O8 phases were created. These phases increased melt viscosity and improved foamability. The effect of physical properties, foam structure, alloy microstructure, pore size, and distribution on the mechanical behavior of metal foams was investigated in the present study. The foam with 8 wt% Si showed minimum density and maximum foamability, while it possessed a complete peak of stress. Thinner cell walls in Al–Si foams were observed, which could be attributed to the effect of silicon on melt's surface tension. Results suggested that foams with 0 and 8 wt% Si are suitable for use as an energy absorber. [ABSTRACT FROM AUTHOR]

6XXX series aluminum alloys are generally excellent alternatives to steels for many forged parts in aerospace and automotive industries. In this study, the forging performance of the 6082 aluminum alloy is investigated in order to replace the existing material for forged steel parts. The effect of artificial aging of the alloy on the microstructure and mechanical properties is studied. Optimum aging conditions are determined. Results reveal that AA6082 could be a good replacement for applications where shock and vibrational loads exist. The rod end automotive part currently manufactured from AISI1045 can be replaced by AA6082 without any design changes. The major drawback is that the cold forging of the aged alloy is poor due to its brittle nature and crack initiations. Therefore, warm or hot forging is recommended to overcome the poor forgeability. [ABSTRACT FROM AUTHOR]

A near eutectic Al-12.6Si alloy was developed with 0.0wt%, 2.0wt%, 4.0wt%, and 6.0wt% Al-5Ti-1B master alloy. The microstructural morphology, hardness, tensile strength, elongation, and fracture behaviour of the alloys were studied. The unmodified Al-12.6Si alloy has an irregular needle and plate-like eutectic silicon (ESi) and coarse polygonal primary silicon (PSi) particles in the matrix-like α-Al phase. The PSi, ESi, and α-Al morphology and volume fraction were changed due to the addition of the Al-5Ti-1B master alloy. The hardness, UTS, and elongation improved due to the microstructural modification. Nano-sized in-situ Al3Ti particles and ex-situ TiB2 particles caused the microstructural modification. The fracture images of the developed alloys exhibit a ductile and brittle mode of fracture at the same time. The Alα5Tiα1B modified alloys have a more ductile mode of fracture and more dimples compared to the unmodified alloy. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is an emerging solid-state technique for preparing surface composites using various reinforcements. Ceramics and metallic particles are easily reinforced in a matrix by this technique. Surface composites made from an LM24 alloy reinforced with graphite and tin, with good wettability and material flow owing to the low melting point of tin, were fabricated by FSP at two rotational speeds of 1,400 and 1,000 rpm. Despite its low hardness, the graphite/LM24 surface composite fabricated at a higher rotational speed of 1,400 rpm exhibited better wear resistance. However, its frictional behavior was not significantly affected by the reinforcement. The fabricated surface composites with graphite and tin reinforcement as well as graphite-only reinforcement exhibited contradicting behaviors under sliding wear conditions. The post wear analysis indicated that abrasion, adhesion, layer formation, and delamination occurred on the composite surfaces. [ABSTRACT FROM AUTHOR]

Porous nitrogen–doped-carbon-coated nano-Si/graphite ternary composites were prepared by liquid-phase stirring, high-temperature calcination, and acid etching. At the Si and graphite mass ratio of 1:5 in the ternary composites, porous nitrogen–doped-carbon-coated nano-silicon particles were uniformly distributed into the graphite framework, which not only acts as active material for lithium storage but also provides high conductivity for Si particles. The porous amorphous nitrogen–doped carbon shells could further enhance both lithium ion and electrical conductivity of the composite and could also effectively relieve the volume expansion. The composite anode exhibited a highly stable specific capacity of 500 mAh g−1 after 1000 cycles with the capacity retention of 95.5% at a high current density of 2000 mA g−1. It also delivered a good rate performance of 739, 662, 589, and 507 mAh g−1 at the current densities of 300, 500, 1000, and 2000 mA g−1, respectively. [ABSTRACT FROM AUTHOR]

Al-18%Si-4.5%Cu alloy was processed by route BC equal-channel angular pressing (ECAP) at a temperature of 400 °C. Electron backscattered diffraction (EBSD) was used to analyze the microstructure and microtexture during the ECAP process. The microstructural results showed three important effects: First, the particle-stimulated nucleation (PSN) and continuous dynamic recrystallization (CDRX) had the main effect on the refinement of the aluminum matrix during the ECAP process. Second, after the third and fourth passes, due to redundant strain created by route BC, the heterogeneous microstructure was observed. Third, further ECAP passes led to further fragmenting and better distribution of the particles. The microtextural results showed that further ECAP passes led to strengthening the B / B ¯ component at the center and also strengthening the A*1 and A*2 components at the bottom of specimens. The microhardness results showed that the grain refinement strengthening and precipitation strengthening were the main strengthening mechanisms in the route BC-ECAPed Al-18%Si-4.5%Cu alloy. [ABSTRACT FROM AUTHOR]

The surface of AK5M2 (Al–Si) alloy is treated with an intense pulsed electron beam in various modes (accelerated electron energy of 17 keV, electron-beam energy density of 10, 20, 30, 40 and 50 J/cm2, pulse duration of 50 and 200 μs, the number of pulses 3, and the pulse repetition rate 0.3 s–1). Microhardness analysis is performed, and the elemental and phase composition and state of the defect substructure of the surface layer are studied by scanning electron microscopy and X-ray phase analysis. It is shown that the increase in microhardness of the Al-Si alloy is due to the formation of a submicrometer-sized structure of high-speed cellular crystallization, the enrichment of an aluminum-based solid solution with alloying and impurity elements, and the reprecipitation of nanoscale particles of strengthening phases. It is suggested that the higher values of the microhardness found in the alloy irradiated at 50 J/cm2 and 50 μs compared with the alloy irradiated at 50 J/cm2 and 200 μs are due to the process of tempering the material, which have a greater development with a longer duration of exposure to beam electrons per pulse. [ABSTRACT FROM AUTHOR]

The separation behaviour of primary silicon from high-silicon Al-Si melts during the directional solidification under alternating electromagnetic field with varying frequencies and pulling rates is investigated. Results show that the separation of Si from Al-Si melts significantly depends on the electromagnetic frequency and the solidification rate of the melts as well. Moreover, the separation and enrichment effects of Si electromagnetic frequency with 3 kHz was superior to 30 kHz during the electromagnetic separation process, which was independent on the initial concentration. The flat and distinct separation interfaces could be formatted by using a relatively low pulling rate of 5 μm/s and a frequency of 3 kHz. Finally, the differential scanning calorimetry analysis showed that the alloy section had good thermal stability in the whole electromagnetic separation process. This method has the prospect and potential of becoming the method for manufacturing low-cost Al-Si alloys after the electrothermal process. [ABSTRACT FROM AUTHOR]

Mg alloys have been known as the lightest metal materials. However, their practical use is strictly limited due to their poor corrosion and wear resistances. To improve those resistances simultaneously, the present authors have fabricated an Al-Si alloy coating on a Mg alloy substrate by hot extrusion. The Al-Si alloy for coating material was prepared by powder metallurgy and casting processes. An AZ80 Mg alloy billet, a compacted Al-Si alloy plate or a cast Al-Si alloy plate, a die and rams were put in bottom of an extrusion container, and the Mg alloy and the Al-Si alloy were indirectly extruded together. By the hot extrusion, the Mg alloy was successfully coated with the Al-Si alloys prepared in both the powder metallurgy and the casting. The Al-Si alloy-coated Mg alloys showed a high corrosion resistance in a 1.0 mol/L HCl aqueous solution. Also, the wear resistance of the Mg alloy was significantly improved by the Al-Si alloy coating layers. The highest wear resistance was obtained with a cast Al-20 vol.%Si alloy coating layer. The coating improved the wear resistance by 50% compared with the AZ80 Mg alloy. [ABSTRACT FROM AUTHOR]

The paper concerns the mechanical properties of hypoeutectic Al-Si alloy (silumin) with the addition of Cr, Mo, V and W. Changes in microstructure under the impact of these elements result in a change in the mechanical properties. Crystallization of Al-Si alloys determines grain size reduction, which causes a significant increase in their strength properties. Crystallization subjected to modifications through the influence of alloying additives can be described by the cooling curve run. Statistical relationships between the characteristic values of cooling curves and mechanical properties are investigated with data mining techniques of regression, especially regression trees. Such knowledge could provide an ability of a property prediction on the basis of cooling curves in terms of the benefits of a short time of the curve registration. [ABSTRACT FROM AUTHOR]

This review covers research aimed at finding the optimum composition and growth rate to obtain a highly modified Al-Si alloy using directional solidification. Investigations of microstructure and mechanical properties as a function of Si content and growth rate are analyzed. These works show that the composition yielding a eutectic microstructure changes considerably with increasing solidification rate in the range of 102-104 μm/s. The increase in ultimate tensile strength with increasing Si content up to that giving a completely eutectic microstructure is explained by a redistribution of volume content of α-Al and eutectic. The increase in tensile strength with increasing rate is explained by a decrease in microstructural scale accompanying the transformation of flake-to-fiber eutectic microstructure. The optimal fine fiber structure without any primary crystals of Al-Si alloy at a given Si content is obtained at the solidification rate giving a completely eutectic microstructure at that composition. Hypereutectic alloys can be fully modified using rapid cooling at such solidification rate that causes coupled growth of the eutectic for given composition of the alloy. Additional Sr modification results in a super-modified structure, high tensile strength and record high elongation. [ABSTRACT FROM AUTHOR]

An investigation was carried out to determine the effect of nickel on the microstructure, hardness and wear behaviour of surface alloying on aluminium–12%silicon alloy. The heat source utilized for modifying the surface was gas tungsten arc. Two hundred-micrometre-thick Ni–P coating was pre-deposited using electroless process on the aluminium–12%silicon alloy substrate. The surface alloying process was performed on the coated surface. By using microhardness tester and pin-on-disc wear testing machine, the hardness and wear rate of the modified layer were calculated, respectively. A refined grain structure was observed with the fusion of Ni in the alloyed layer. That was attributed to the rate of cooling in the modified layer. As a result of nickel addition, the hardness was improved and wear rate was found to decrease. [ABSTRACT FROM AUTHOR]

Hypereutectic Al–13.5Si alloy containing 1.47% of copper and 1.30% of magnesium was designed as a potential material for internal combustion engine pistons. The optical microscopy and scanning electron microscopy (SEM) revealed the fine dendrites of α-Al phase and significantly dispersed eutectics in as-cast specimens. Several intermetallic phases were observed indicating different crystallization velocities and alloy composition nonuniformities. The tensile testing and hardness measurements performed at room temperature have shown an excellent tensile strength and hardness of as-cast specimens, but low elongation due to a complex multiphase structure. The mechanical examinations at 250 °C and 300 °C have presented a decrease in tensile strength and an increase in elongation, while hardness was slightly changed. The fractographic analysis has shown the features of the brittle as well as ductile fracture. The areas of dimples and areas containing particles with smooth surfaces were detected. Electrochemical methods, Tafel linear polarization, cyclic voltammetry, chronoamperometric measurement and impedance spectroscopy were employed to determine the corrosion behavior of as-cast specimens in 0.5 M NaCl solution. The resistant oxide layer formed on the surface was not entirely consistent due to the appearance of intermetallic phases. SEM examinations of corroded samples did not discover severe pits on their surfaces. [ABSTRACT FROM AUTHOR]

To fabricate a low-reflectance aluminum alloy, we have analyzed the changes in reflectance according to the morphology, components, and composition of the aluminum alloy. We find that the larger the particle size of the powder, the lower is the reflectance. This is attributed to the fact that the larger the particle size, the greater is the amount of light absorbed into the interparticle space in the powder. In addition, the reflectance decreases with increase in the Si and Mg contents, because of the lower reflectance of the strengthening phase formed in the alloy as compared to that of aluminum. In contrast, lanthanide addition causes an increase in the reflectance, which is attributed to an increase in the electrical conductivity of the alloy. [ABSTRACT FROM AUTHOR]

The 700 °C isothermal section of an Al-B-P ternary system was analyzed by scanning electron microscopy coupled with an energy dispersive spectrometry and x-ray diffraction. The Al-1.5B-3P master alloy, designed based on the phase diagram, was used for the modification of a eutectic Al-Si alloy. The results revealed the presence of five three-phase regions in the 700 °C isothermal section of Al-B-P ternary system, namely, Liq. + AlB2 + AlP, AlB2 + AlP + BP, AlB12 + AlB2 + BP, AlB12 + BP + α-B and AlP + BP + Pgas. The phase constituents of the Al-1.5B-3P alloy are the Al, AlB2 and AlP phases. After complex modification by the Al-1.5B-3P alloy, a large number of fine α-Al dendrites and some primary Si formed in the eutectic Al-Si alloy. The morphology of eutectic Si changed from a needle-like to granular or short rod form. Compared with the unmodified eutectic Al-Si alloy, the tensile strength and elongation of the alloy modified with 0.4% Al-1.5B-3P were increased by 20 and 24%, respectively. Overall, the comprehensive mechanical properties of the modified alloy were significantly improved. [ABSTRACT FROM AUTHOR]

Abstract The properties of hypoeutectic Al–Si alloy (silumin) with the addition of elements such as Cr, Mo, V and W are described. Changes in silumin microstructure under the impact of these elements result in a change of the mechanical properties. The research includes presentation of procedure for the acquisition of knowledge about these changes directly from experimental results using mixed data mining techniques. The procedure for analyzing small sets of experimental data for multistage, multivariate and multivariable models has been developed. Its use can greatly simplify such research in the future. An interesting achievement is the development of a voting procedure based on the results of classification trees and cluster analysis. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is a novel process for refinement of microstructure, improvement of material’s mechanical properties and production of surface layer composites. In present investigation, composite reinforced with using Zn/ MoS2 powder in as-cast alloy were developed at tool rotational speed of 664 rpm and tool transverse speed of 26 mm/min using FSP. Microstructural observation of MoS2/Zn reinforced composites confirmed the fine and equiaxed grains in the stir zone (SZ) and distribution of fine reinforced particles of MoS2/Zn in SZ. Moreover, agglomeration of MoS2/Zn particles were not observed. The ultimate tensile strength was measured to be 113 ± 9 and 82 ± 7 MPa for MoS2and Zn reinforced Al-Si alloy, respectively. The sliding wear was studied using pin-on-disk tribometer and it was found that FSP enhanced the wear resistance of the as-cast alloy. The MoS2 reinforced composite showed superior wear resistance than Zn reinforced composite and base material. To understand the acting wear mechanism, the field emission scanning electron microscope (FESEM) of worn out surfaces were performed. [ABSTRACT FROM AUTHOR]

Increasing environmental demands are forcing the automotive industry to reduce vehicle emissions by producing more light-weight and fuel efficient vehicles. Al-Si alloys are commonly used in automotive applications because of excellent castability, high thermal conductivity, good wear properties and high strength-to-weight ratio. However, most of the aluminium alloys on the market exhibit significantly reduced strength at temperatures above 200 °C. This paper presents results of a study of the effects of Co and Ni in a hypoeutectic Al-Si alloy on microstructure and mechanical properties at room and elevated temperature. Tensile test specimens with microstructures comparable to those obtained in high-pressure die casting, i.e. SDAS ~ 10 µm, were produced by directional solidification in a Bridgman furnace. The results show an improvement in tensile properties up to 230 °C. [ABSTRACT FROM AUTHOR]

The refinement potential of Al-3.5FeNb-1.5C master alloy on pure aluminium and Al-9.8Si-3.4Cu alloy has been investigated. Different amounts of Al-3.5FeNb-1.5C master alloy were added to estimate the optimal addition level. It was found that the addition of Al-3.5FeNb-1.5C grain refiner can promote significantly the refinement of grains in the pure aluminium, particularly at 0.1wt.%, with the mean primary aluminium α-grain size reducing to 187±3 µm from about 1-3 mm. Similarly, the microstructural study of the Al-9.8Si-3.4Cu alloy die casting at different weight percentages (viz. 0.0wt.%, 0.1wt.% and 1.0wt.%) of Al-3.5FeNb-1.5C master alloy shows that the Al-3.5FeNb-1.5C master alloy as a grain refiner is also acceptable for Al-Si cast alloys when the silicon content is more than 4wt.%. As a result of inoculation with Al-3.5FeNb-1.5C master alloy, the average grain size of α-Al is reduced to 22±3 µm from about 71±3 µm and grain refining efficiency is not characterized by any visible poisoning effect, which is the major limitation in the grain refinement of Al-Si cast alloys by applying Al-Ti-B ternary master alloys. Mechanical properties such as ultimate tensile strength and yield strength are significantly improved by 9.6% and 9.7%, respectively. [ABSTRACT FROM AUTHOR]

The distribution characteristic and segregation behavior of metal impurities during directional solidification of Al-20Si, Al-30Si and Al-40Si alloys have been investigated. The morphologies of the alloys and impurity phases were observed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The concentration profiles of representative metal impurities Al, Fe and Ti were measured by inductively coupled plasma optical emission spectrometry. The results indicate that the metal impurities segregate into the eutectic Al-Si melt during the growth of primary Si flakes and gradually segregate towards the top of each ingot during directional solidification. A concept of apparent segregation coefficient is proposed to characterize the segregation behavior of impurity elements. The apparent segregation coefficients of metal impurities decrease with increase in solidification temperature of the Al-Si alloys. [ABSTRACT FROM AUTHOR]

Overcoming general brittleness of hypereutectic Al-Si alloys is in urgent need for expanding their application in automotive, aerospace and construction industries. A unique phenomenon was observed that bulk ultrafine-grained Al-26 wt.% Si alloy, produced by severe plastic deformation via equal-channel angular pressing, exhibited higher toughness at the impact temperature of − 196 ~ 100 °C than the coarse-grained casting alloy. The improvement in impact toughness at all testing temperatures was mainly due to the homogeneous ultrafine-grained structure with the breakage of brittle primary silicon crystals, which generated more and deeper fracture dimples that consumed much higher fracture energy. It indicates the advantage of bulk ultrafine-grained Al-Si alloys and spurs their application interest at various ambient temperatures. [ABSTRACT FROM AUTHOR]

Fe-rich intermetallics, especially β-Fe phase, usually forming in the microstructure of cast aluminum alloys, are very detrimental to mechanical properties. In the present work, the effects of Fe content on phase transformation and microstructures were analyzed using a 3D X-ray microscope. Based on the high-resolution 3D X-ray computed tomography, the 3D characteristics of Fe-rich intermetallics and micropores in the gravity-cast Al-6Si alloys with different Fe contents were investigated. In addition, the effect of intermetallics on the microporosity was discussed. The results show that with increasing the Fe content from 0.10wt.% to 0.60wt.%, the volume fraction of Fe-rich intermetallics and the volume of the largest size Fe-rich intermetallic increased, and the 3D morphology of intermetallics changed from fine flake to network aggregation. As the Fe contents increased, the shrinkage pores were characterized, which were rather complex due to the micropores promoted by the intermetallics interactions. [ABSTRACT FROM AUTHOR]

Al–(12, 20, 35 wt%)Si alloys were fabricated using powder metallurgy process involving hot pressing followed by hot extrusion. The effect of Si content on the microstructure [by scanning electron microscopy], the mechanical properties (hardness and tensile tests), and the thermal expansion behavior were studied in detail, respectively. Due to the friction between the Si phase and the matrix, as well as the diffusion of the Si atoms, the Si phase becomes a particulate shape after hot extrusion, and the size increases with increasing Si content. The mechanical strength increases, whereas, the elongation decreases with increasing the Si content from 12 to 35 wt%, which lead to a variation of the fracture mechanism from ductile to brittle failure. The coefficient of thermal expansion (CTE) decreases with increasing Si content as a result of restriction of Si on the Al matrix, and the measured CTE value is in good agreement with the Turner model below 573 K. [ABSTRACT FROM PUBLISHER]

In this article, the results of investigations of abrasive wear resistance and wear under the fretting of the samples obtained by the method of laser microcladding have been presented. The material for sample preparation was powder of Al-Si hypereutectic alloy with the following composition: 70-74 wt % Al and 26-30 wt % Si. The influence of the structure and phase composition of AlSi30 alloy on wear resistance under the conditions of abrasive wear and wear under fretting conditions has been shown. [ABSTRACT FROM AUTHOR]

This study investigated the effect of heat treatment on tensile and high-cycle fatigue deformation behavior of extruded Al-12 wt%Si alloy. The material used in this study was extruded at a ratio of 17.7: 1 through extrusion process. To identify the effects of heat treatment, T6 heat treatment (515 °C/1 h, water quenching, and then 175 °C/10 h) was performed. Microstructural observation identified Si phases aligned in the extrusion direction in both extruded alloy (F) and heat treated alloy (T6). The average grain size of F alloy was 8.15 °C, and that of T6 alloy was 8.22 °C. Both alloys were composed of Al matrix, Si, AlCu, AlNi and AlFeSi phases. As T6 heat treatment was applied, AlCu phases became more finely and evenly distributed. Tensile results confirmed that yield strength increased from 119.0 MPa to 329.0 MPa, ultimate tensile strength increased from 226.8 MPa to 391.4 MPa, and the elongation decreased from 16.1% to 5.0% as T6 heat treatment was applied. High-cycle fatigue results represented F alloy's fatigue limit as 185 MPa and T6 alloy's fatigue limit as 275 MPa, indicating that high-cycle fatigue properties increased significantly as heat treatment was conducted. Through tensile and fatigue fracture surface analysis, this study considered the deformation behaviors of extruded and heat treated Al-Si alloys in relation to their microstructures. [ABSTRACT FROM AUTHOR]

In the present research, the Al-Si alloy surface is treated by KrF excimer pulse laser for different number of laser pulses in ambient condition at energy 4.75 J/cm. The surface microstructural characterization was done by the optical microscope, in situ video recording during laser pulsing, SEM and TEM. The fretting wear test was undertaken to assess the tribological behavior. In situ video recording showed changes in the surface reflectivity with the number of pulses which is related to progressive changes in the surface compositional homogeneity. After ten pulses, signs of rippled structure were observed. The 15 pulse samples showed star-like morphological feature at the central region. The TEM observations showed high density of stacking faults/twins in Si after first pulse treatment. After 15 pulses, nano-crystalline Si precipitates in the size range <5 nm are seen to be homogeneously distributed. A cellular structure with the cell size <100 nm formed in the matrix. These cell boundaries were decorated with the Si nanocrystals. A positive effect in wear resistance property is observed after the 15 pulses treatment. [ABSTRACT FROM AUTHOR]

Iron is generally regarded as an unavoidable impurity in Al-Si casting alloys. The acicular Al3Fe and β-Al5FeSi (or Al9Si2Fe2) are common iron-containing intermetallic compounds (IMCs) in conventional structure which have a detrimental impact on the mechanical properties. In this paper, ultrasonic field (USF) was applied to modify acicular iron phases in Al-12%Si-2%Fe and Al-2%Fe alloys. The results show that the USF applied to Al-Fe alloys caused the morphological transformation of both primary and eutectic Al3Fe from acicular to blocky and granular without changes in their composition. In the case of Al-Si-Fe alloys, ultrasonic treatment led to both morphological and compositional conversion of the ternary iron IMCs. When the USF was applied, the acicular β-Al9Si2Fe2 was substituted by star-like α-Al12Si2Fe3. The modification rate of both binary and ternary iron IMCs relates to the USF treatment duration. The undercooling induced by the ultrasonic vibration contributes to the nucleation of intermetallics and can explain the transformation effect. [ABSTRACT FROM AUTHOR]