ABSTRACT: Wear behavior of spray formed Al-17Si and Al-17Si-10Sn alloys was investigated using a pin on disk type wear testing machine and characterization of this Al-Si and Al-Si-Sn metal matrix composite alloys is done using optical microscope. The alloys were spray formed in an environmental chamber using nitrogen gas and a deposition distance of 380mm. The spray formed alloys showed considerable microstructural refinement with uniform distribution of Si particles in Al–Si alloys and that of Sn and Si particles in the matrix of primary Al phase of Al–Si–Sn alloys. Dry sliding wear behavior of these metal matrix composite alloys was studied as a function of sliding distance, applied load and sliding velocity. The wear response parameters such as wear rate and frictional force were measured. A considerable increase in the wear resistance of the alloy is observed with addition of Tin(Sn). The improved wear properties and characterization of the alloy containing Sn are discussed in light of the microstructural features of spray formed alloy.
Alloy which is defined by metallic bonding character is a mixture of two or more metals or non- metals exhibiting different phases used to enhance the properties such as tensile strength and shear strength better than those of their parent metal. In this study we typically use Aluminum as a base alloy, the reason behind selecting this metal is due to its high strength to weight ratio, low density these properties as a function help the metal to incredibly use in manufacturing industries especially in aerospace and marine applications (Balamugundan and Karthikeyan, 2014) and when this metal is mixed with silicon as weight percentage there will be change in their physical properties like reduction in thermal expansion, magnetic susceptibility, mach inability (www.kettometals.com, 2001). The increase of Silicon content into the Aluminum mixture will increase the fluidic nature of the alloy which helps in casting applications. These properties of Al-Si alloy help them to use in manufacturing automobile parts like pistons, cylinder liners, cylinder heads. At high silicon levels, the alloy exhibits excellent dimensional stability, surface hardness and wear resistant properties (Jonathan, 2003). The main reason of Aluminum's weaknesses is its lack of strength is its pure form. To get around this and preserve Aluminum's low density and *Corresponding author: Sai Sandeep, N.V.
cross sectional profile was taken to calculate the wear loss. ........................................................ 97 Figure 3. 11: Discretization of 3D model of a silicon particle embedded in aluminum matrix – (a) top view and (b) left side view – the discretization density in the vicinity of the Al-Si interface is shown. The mesh density near the interface indicated by the dotted square is shown in (c). ..... 98 Figure 3. 12: A typical work flow to convert 3D image to 3D FE model using ScanIP. Segmented mask represents the process of identifying different regions within volume of interest. In the multi-particle model the two segments are the aluminum matrix and the silicon particles. ....... 99 Figure 3. 13: (a) SEM image of the volume of interest (VOI) in Al-12.6% Si alloy from where 2D parallel images spaced between 100 nm were sectioned using FIB; (b) the first section from the VOI showing silicon particles and the aluminum matrix; (c) three principal views of the section from b showing the segmentation of aluminum matrix and silicon particles; (d) volumetric voxel mesh (mesh lines are not shown) and the mesh refinement regions; (e) and (f) final model of the microstructure from Figure 3. 13a with and without the mesh lines, respectively. Silicon particles are numbered with subscripts in (c) and (d) for easy identification of them. ............................. 100 Figure 3. 14: The silicon particle loading-unloading cycle to simulate sinking-in in single-particle model. .......................................................................................................................................... 103 Figure 3. 15: Variation in COF during a lubricated pin-on-disk test using Al-12.6% Si alloys at 2.0 N load; static COF, μ S =0.2 and average dynamic COF, μ D =0.1 were used in the simulation. 104
Large-area EBSD misorientation maps were acquired on the four alloys and are presented in Supplementary Fig. S3. Different grain colors indi- cate misorientation greater than 5°. From these maps it can be noted that, in unmodified Al-Si, the primary Al dendrite orientation extends within the eutectic Al. This indicates that the solidification of the eutectic Al occurred mainly on primary Al dendrites. There are also some areas in the Al-Si map that seem to have nucleated separately from the primary dendrite, but when comparing the Al-Si EBSD map with the Al-Si-Sr one, a stark contrast can be noted immediately. The latter shows com- plete separation between the primary and eutectic Al, as individual areas within the eutectic have different orientations relative to each other and relative to the primary. In the Al-Si-Ce and Al-Si- Ce-Sr alloys, though not as evident primarily due to
Some aluminium alloys are quite important materials used in the manufacturing of various parts, predominantly in automotive, transport, aviation and aerospace sectors, in order to lower emissions that are harmful to the environment (SO X, CO 2 , and NO X emissions) and to use en- ergy resources efficiently through weight de- creases [2, 3-6]. Within this scope, among the significant aluminium alloys most commonly used in today’s industries is Al-Si alloys [4, 7, 8, 10]. It is observed that the studies conducted on aluminium alloys generally focus on such subjects as microstructure and mechanical prop- erties analyses, hardness and creep properties
In the last several decades global efforts by the metal casting academic and industrial communities were not fully successful in converting ultra-strength aerospace engineering materials like the B206 Al-Cu alloys or the 7000 series Al-Zn alloys to cast components used by other transportation industries (i.e. automotive). In addition, there is a lack of research on the development of nano and ultra-fine cast Al-Si-Cu materials with characteristics comparable to and/or exceeding ultra-high aerospace ones. Major problems with the first two materials are: corrosion and solidification hot tearing. Attempts aiming at the development of nano aluminum cast alloys are limited to the high purity Al-Si system tested using directional solidification. This methodology is very difficult for mass cast component(s) production in the automotive industry.
continued to be performed during the past decades, there are a lack of precise information and comprehensive under- standing in high Fe region of the ternary system. The main purposes of the present study are to predict the solidiﬁcation path and phase formation based on the thermodynamic analysis and to verify the predicted results experimentally. The present paper reports the eﬀects of Fe content and cooling rate on those phase formation sequence in Fe- containing eutectic Al-Si alloys. The paper also reports the
Although there is good agreement about the eﬀect of Fe on the microstructure of the Al-Si cast alloys, there are inconsistencies in the reports of investigations into the inﬂuence of Fe on the mechanical properties of the castings. 1,11) Fe has usually been thought to be detrimental because the Fe-rich intermetallic compounds are generally thought to be brittle. They are assumed to act as stress raisers and are points of weak coherence, causing reduction in mechanical properties, particularly reducing the ductility of cast alloys. The reduction of mechanical properties depends on their amount, size and type. Among the three main types of Fe-rich phases in Al-Si cast alloys, -Fe only dissolves limited amounts of other elements like Mn and Cu. It usually appears as highly faceted platelets (appearing as needles in 2- D sections), extended even up to several millimetres long. The -Fe phase, therefore, has been identiﬁed as the Fe phase that causes the most serious loss of strength and ductility in Al-Si alloy castings. 10,12)
The melting behavior of the Pb NCs was monitored by a similar diffractometer equipped with a high-temperature attachment which allows measurements up to 1273 K. Symmetric θ–2θ scans with a scan speed of 0.6°/min were employed to monitor the diffraction signals from Pb NCs. The sample was mounted on a molybdenum base furnace and kept in a He gas flow in order to reduce the temperature gradient from the heater to the sample surface. The temperature was calibrated with an accur- acy of ±2 K by recording the Au-Si and Al-Si eutectics at 636 and 850 K, respectively. The sample was heated to each temperature at a heating rate of 5 K/min and held for 2 min before collecting the XRD profiles. Dur- ing the measurements, the temperature stability was approximately 0.2 K.
From the Platelet Distribution Maps, it can be seen that platelets in untreated sand mold with low strontium content are concentrated between β = 0.3 and 0.5. Untreated High Strontium Al-Si Eutectic Alloy in metal mold however, have platelets with their sphericities largely between β = 0 and 0.3 and distributed to the left pane of the chart.
The present work deals with a novel approach of fabricating harmonic structure in Al alloy through the application of semi-solid reaction between Al and Si. The harmonic structured Al was prepared by powder metallurgy route, where the Al and Si powder were subjected to con- trolled mechanical milling followed by subsequent spark plasma sintering to make a compact. The sintered compact resulted in a network structure of hard interconnected silicon dispersed region combined with Al-Si solid solution phase, known as shell, enclosing the soft phase of pure aluminum matrix known as core. The harmonic structured Al compact demonstrated retention of both uniform and total elongation as compared to its heterogeneous bimodal structure counterpart, which is the typical feature of the harmonic structured material. The application of semi-solid reaction between Al and Si in fabricating harmonic structure proved to be effective in improving mechanical properties of Al alloy. Present work also discusses the deformation behavior of the sintered compacts, with respect to its strain hardening behavior.
hypoeutectic Al-Si alloys were studied based on thermodynamic analysis and pertinent experiments. The thermodynamic calculations were performed using the Thermo-Calc program. For analyses in the high alloy region of the Al-Si-Fe ternary system, a thermodynamic database for Thermo-Calc was correctly updated and revised by the collected up-to-date references. For thermodynamics-based predictions of the solidiﬁcation path in Fe-containing hypoeutectic Al-Si alloys, liquidus projection (including various invariant, monovariant, and bivariant reactions and isotherms) and equilibrium phase fraction were calculated as functions of composition and temperature in the Al-Si-Fe ternary system. The calculated results were compared to experimental results using various casting runs. In order to analyze the solidiﬁcation path as a function of Fe content, two representative hypoeutectic Al-Si alloys with diﬀerent Fe levels were designed. To better understand the inﬂuence of cooling rate on the formation behavior of the phase, the two alloys were solidiﬁed under slowly- and rapidly-cooled conditions, respectively. The cooling curves of the solidiﬁed alloys were recorded by thermal analysis and various important solidiﬁcation events were detected using the ﬁrst derivative of the cooling curves. Microstructures of the casting samples were studied by combined analyses of optical microscopy (OM) and scanning electron microscopy (SEM). For the slowly-cooled condition with the high Fe level, the primary phase enveloping the Al 8 Fe 2 Si ()
has been reported that the fracture of primary Si which is located near the cutting edge during machining caused chip breaking and increased the tool wear in hypereutectic cast Al- Si alloys. 3,4) Since cast Al-Si alloys are widely used as components for engines, and machining is needed after casting to obtain a certain precision, several studies have been conducted on the machinability of cast Al-Si alloys. 3) However, most of these studies have investigated tool wear as a function of machinability. Since cast Al-Si alloys have great chip breakability, the investigations did not focus on the chip breaking mechanism in cast Al-Si alloys.
The Al-Si alloy with near eutectic composition has been conventionally used as a piston material for automobile applications. It is required to possess high abrasive wear resistance for enhanced life of the engine. The alloy is known to have fairly good wear resistance due to increased percentage of silicon present in fine form. In the present investigation, Al-SiC particulate composites have been studied for their wear resistance against emery paper (400 grit SiC particles) counterface and a comparison has been made with existing piston alloy i.e. Al-Si alloy.
This work involves applying the coating by nanoalumina using atomization technique to improve corrosion resistance of pure Al, Al-Si and Al-Zn alloys. Potentiodynamic polarization method was carried out for uncoated and coated specimens in 3.5% NaCl solution at room temperature. Corrosion parameters were measured to know the protection efficiency obtained for nanocoatings. The data of corrosion indicate that nanoalumina coatings corrosion potentials shift toward active direction and corrosion current densities toward lower values. Good protection efficiency was obtained especially for coated pure Al equal to 80%.
about 0:2 GPa for d between 100 and 200 nm, and falls between 0:2 GPa and þ0:2 GPa for d < 100 nm thick. 20) Such strong compressive internal stress in the as deposited state for sputtered ﬁlms may be associated with a shot peening eﬀect by sputtered atoms. On the other hand, intk þ0:5 GPa was observed for Al-Si(Cu) sp ﬁlms after
adsorbed at metal surfaces where they inhibit oxygen reduction; inhibit pit initiation of Al and dissolution of active intermetallic phases in Al alloys; modify the chemical composition of the surface of passive oxides and passivated intermetallic phases by adsorption and buffering; adsorb on aluminum oxides, lowering the zeta potential, thereby discouraging adsorption of anions chloride, which promote dissolution and destabilization of protective oxides.
The as-cast samples were partially remelted and isothermally held in the semisolid region at 570°C for 10 min. Figure 2 shows the semisolid microstructures of the Al-Si alloy with and without AlP refinement after isothermal holding. The microstructure suggests that the materials were about 40% solid at the holding temperature and the rest was liquid which had been remelted from the Al-Si eutectic. Both primary Si and primary Al co-existed as the solid and they were uniformly distributed in the liquid Al-Si eutectic. The primary Si structure did not change much from the as-cast condition. The particles were at a similar size to the as-cast materials, and the morphology remained polyhedral but slightly rounded. The primary Al dendrites, on the other
In the automobile industry, efforts have been concentrated to minimize the energy consumption and reduce the environ- mental impact. In addition, fabrication of structural bodies involve, in most instances, the application of a joining pro- cess, that is, combining one part with another. For such social demands, an important group of aluminum alloys would be 6000 series aluminum alloys, which constitute the Al–Mg– Si alloy system. Al–Mg–Si alloys are the commercial alloys, which have been widely used as materials for welded struc- tures. Usually welded Al–Mg–Si alloys have some problems, such as low fracture toughness in the heat-affected zone near a weldment due to liquation cracking. 1) The existence of liqua- tion crack has a negative effect on the mechanical properties. To characterize the effects of the defects, toughness of the weld metal is usually evaluated using notched specimens. In a previous paper, 2) it became clear that using A5356 as a filler with addition of small amount of Mn is effective to suppress recrystallization, which leads the drastic decrease in fracture toughness by liquation crack. Another type of filler, A4043 (Al–Si wire) is also used. It is interesting to compare the re- sult with that of A5356 filler, especially the effect of Mn ad- dition. In the present research, the toughness tests of welded materials were carried out using the instrumented Charpy im- pact testing machine. Particular emphasis is placed on the determination of toughness of base material and the welded metal using the two types of fillers A4043 and A5356. In ad- dition, for the base metal, tensile tests were carried out and fracture surfaces were also examined.
Ca/(Al + Si) ≤ 1.5 and Al/Si > 0.1. 29,30 C-(N,K-)A-S-H phases are also major reaction products in ∼2000 year old Roman cements. 31 Incorporation of alkali species into the interlayer region and on external surfaces of C-(N,K-)A-S-H is believed to occur via a charge-compensation mechanism (Fig. 1), 11,19,32,33 with less associated alkalis at higher Ca/Si ratios (similar to C-(N,K-)S-H), 34 although no consensus exists regarding the exact mechanism of alkali uptake in this phase. This is corro- borated by the large variation in existing results reported for Na and K uptake as a function of Al content in C-(N,K-)A-S-H: direct correlations, 33,34 an inverse correlation, 25 and indepen- dent relationships 6,11,35 between these two parameters have been reported. There is also a lack of consensus on the selecti- vity of C-(N,K-)A-S-H structures between Na or K species, with existing publications reporting either no significant di ﬀ erence between uptake of these two alkali types, 8,21,25,34 or some degree of selectivity for K over Na. 11 This clearly demonstrates a need for additional studies to clarify the relationships between the uptake of Na, K and Al in C-(N,K-)A-S-H.