Academic literature on the topic 'Aluminium-Silicon Cast Alloys - Automotive Engines'

Purpose: In the paper, geometric structure of the surface of A390.0 alloy, manufactured using various methods are presented, in combination with EN-GJL-350 cast alloy, which corresponds to parameters used in combustion engines. Design/methodology/approach: Alloy after a modification with CuP10 master alloy and overheating to 920°C for 30 min was analysed, and the results were compared with those of the material without overheating. Roughness studies allowed for defining the influence of technological history on the wear parameters of the alloy. Findings: Analysis of result shows that all investigated properties were improved. Significant differences between the analysed materials were proved during the analysis of friction coefficient and surface topography of wear track. Research limitations/implications: The application of modified by CuP10 aluminium alloy allows to improve parameters such as friction coefficient and wear rate. This property’s causes that this new modified material can be used in many applications where the aim is to reduce friction coefficient as well as wear rate. Practical implications: Improvement the tribological properties as well as reducing the coefficient of friction makes these materials may be used in many applications in the automotive industry such as engine cylinder, engine blocks, etc.. Originality/value: Influence of aluminium modification on chosen tribological properties and friction coefficient have been investigated.

Combustion engine pistons are subject to variable mechanical and thermal loads, and to variable deformations. The article presents the possibilities of using novel composite alloys for the construction of pistons for combustion engines. The novel alloys make it possible to meet high demands, especially for highly load designs, which practically cannot be met by conventional alloys used so far. These high requirements relate to the weight of the pistons, high temperature strength, alloy crystalline structure, abrasive wear resistance, dimensional stability. The requirements for pistons have an impact on the durability of the engine's operation, the level of noise emissions; exhaust gas blow-by into the crankcase, the level of emitted toxic exhaust components, mainly hydrocarbons. The research covered metallography (chemical composition, microstructure), material strength, abrasive wear, and thermal expansion. Investigations of the alloy crystallization process during casting were carried out using the Differential Thermal Analysis (DTA) method. The castings were used for metallographic tests. The strength of the samples was tested at room temperature (20° C) and elevated temperature (up to 350° C) on a testing machine equipped with a special climatic chamber. In particular, the article presents Thermal Derivative Analysis curves and representative microstructures of conventional AlSi12 alloy and the novel composite alloy; dependence of the tensile strength versus temperature for the samples of the novel alloy with various nickel content 2% and 4 %; comparison of the tensile strength for conventional alloy and the novel alloy at ambient and 250° C temperature; comparison of abrasive wear of samples, made of novel aluminium alloy and different cast iron; course of the linear expansion coefficient versus temperature for the conventional AlSi12 alloy with incorrect heat treatment; course of the linear expansion coefficient versus temperature for one of tested silumin alloy which expansion coefficient during sample cooling is smaller than during sample heating; course of the linear expansion coefficient versus temperature for the novel composite silumin alloy, after correct heat treatment. The great benefits of using this novel alloy and the introduction of novel alloying elements (in-Situ) have been confirmed in engine research.

The electrification of automotive powertrains in recent years has been driving the development of internal combustion engines towards reduced volumes with higher power outputs. These changes place extreme demands on engine materials. Engineers employ the computer-aided engineering approach to design reliable and cost-effective engines. However, this approach relies on accurate knowledge of the material deformation and fatigue characteristics during service-like loading. The present study seeks to investigate the effect of dwell times on the deformation and fatigue behaviour of the A356-T7 + 0.5 wt.% Cu alloy used to cast cylinder heads. In particular, we study the effect of dwell time duration at various temperatures. A combined fatigue-dwell testing procedure, with the dwell at the maximum compressive strain, replicates the service conditions. It is found that the material exhibits a stress relaxation behaviour with a decreasing relaxation rate. At lower temperatures, the load level influences the relaxation more than at elevated temperatures. However, the dwell does not significantly affect the hardening behaviour or the life of the tested alloy. Finally, we model the time-dependent material behaviour numerically. The Chaboche model, combined with a Cowper–Symonds power-law, is found to capture the visco-plastic deformation behaviour accurately.

Titanium aluminides intermetallic compounds have received great attention during the past decade, since they have the potential, in aircraft and automotive engines, to replace the high density Ni-base superalloys However, these intermetallics possess poor oxidation properties at high temperatures. Previous studies showed that protective alumina scale formation on γ-TiAl can be obtained by small additions (around 2 at.%) of Ag. In the present study, a number of cast Ti–Al–Si alloys were investigated in relation to transient oxide formation in air at 1300°C. After various oxidation times the oxide composition, microstructure and morphology were studied by combining a number of analysis techniques. The TiAl–Si alloys appear to form Al Ti and Si oxides. However, the formation of silicon oxide at the interface of base metal and scale slows down the oxidation rate significantly.

This work presents the review of locomotives and the future of railway automotive power in Africa. Locomotives down time on account of inadequate spare parts still remains a challenge in African. It is thus, imperative to review the locomotives in African, to establish the current capabilities as well as provide recommendations to bridge the gaps and its extrapolated trends in future. Firstly, the comparison factors were track length, electrified rails, number of locomotives and yearly passengers on each of Egypt, Ghana, Kenya, Nigeria, South Africa and Zambia rails. Secondly, the focus was on engine parameters from literatures and maintenance logbooks of locomotives. From available data, it was found that South Africa and Egypt have more advanced rail system than the rest four selected countries. It was also found that additive manufacturing, 3D printing, ductile cast iron and die-forging can be used to produce the engine body for diesel engine using steel and aluminum alloys while aluminum silicon and tin doped with copper are good for reciprocation mechanisms. And finally, increased reliability of locomotives can be guided by an engine selection matrix, while use of renewable and energy hybridization are needed to meet the expansion of railroads in Africa.

Aluminium alloys are among the most prominent and well known materials used in automotive industries. Nowadays, many vehicles used aluminium engine blocks instead of cast iron to improve fuel efficiency. Among cast aluminium alloys, A319 grade alloys are normally used in automotive industries due to a combination of good fluidity and mechanical strength. In this study, A319 cooling slope rheocasting billets were produced in order to obtain near spherical morphology of primary aluminium phase. The change in the α-Al morphology upon the cooling slope casting was remarkable and the dendritic microstructure was almost replaced by α-Al globules and rosettes. The rheocasting billets were prepared for tensile testing at room temperature. It is found that, the yield strength and elongation of cooling slope rheocasting billets is higher than those from as-cast A319 alloy.

Production of primary Al- alloys belong to heavy source fouling of life environs. Care of environment in industry of aluminium connects with the decreasing consumptions resource as energy, materials, water and soil, with increase recycling and extension life of products. Recycled (secondary) aluminium alloys are made out of Al-scrap and workable Al-garbage by recycling. Applications of these alloys in recent years increase especially in automotive industry (dynamic exposed cast, engine parts, cylinder heads, pistons and so on). Controlling the microstructure of secondary aluminium cast alloy is very important, because these alloy containing more of additions elements, that forming various intermetallic phases in the structure. Improved mechanical properties of secondary alloys are strongly dependent upon the morphologies, type and distribution of the second phases, which are in turn a function of alloy composition and cooling rate. The presence of additional elements as Mg, Mn, Fe or Cu allows many complex intermetallic phases to form, which make characterization non-trivial. A combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM) upon deep etching and energy dispersive X-ray analysis (EDX)) were therefore been used for the various phases identification.

Abstract Aluminum-silicon (Al-Si) alloys have good castability in combination with high corrosion resistance, thermal conductivity, and specific strength, making them a strong candidate for many automotive applications. This article describes the processes used in the production of die-cast AlSi9Mg engine brackets for Volvo trucks, the effects of solution treatment temperature on Si particle size, and the benefits of Mg additions on yield strength and heat treatability.

Aluminium Metal Matrix composites (AMC) are known to be very promising light weight materials with enhanced mechanical properties which are used in various industries [1]. Aluminium metal–matrix composites reinforced with SiC and Al2O3 are used in automotive and aerospace applications due to reduction in weight and increase the engine efficiency and thereby reducing fuel consumption [2]. Replacing cast iron engine components with light-weight Al alloys requires overcoming of the poor adhesion and seizure resistance of Aluminium achieved by dispersing SiC, Al2O3 or graphite particles in aluminium, Considerable reduction in wear and friction can be achieved by the use of these reinforcement particulate [3].

The aluminium alloys are used by the automotive, aerospace industries increasingly because of their numerous advantageous mechanical and chemical properties. Surface roughness measurements are essential in characterization of the features of a machined surface. The most widespread aluminium alloy used in cutting is the die-cast type, alloyed with silicon. Industries prefer using two types of such alloys, the so-called eutectic and hypereutectic alloys reinforced with silicon. In this article the cutting capacities of two die-cast aluminium alloys are examined. The cutting experiments were carried out with design of experiment – DOE (the so-called central composite design – CCD). In the course of the examination three factors were altered (cutting speed – vc, m/min; feed – f, mm; depth of cut – a, mm), and the main surface roughness parameters used in the industries were taken as output parameters. The parameters of the manufactured surface roughness and their deviation in case of different workpiece-materials, tool-materials and edge-materials were analysed with statistical methods. Besides minimizing surface roughness, another important criterion of the manufacturing system (machine – tools – chuck – workpiece) is its surface roughness maintaining capacity, which was analyzed with coefficient of variation (CV).

The compression behavior of a newly developed near eutectic Al-Si based cast alloy with three different microstructures has been investigated in the present work. Microstructures with modified and unmodified Si particles and matrix with different tempers are investigated. The main objective of this work is to understand the effect of heat treatment and modification on the fracture behavior of the alloy under compression. This alloy is subjected to compressive loading at different strain rates and temperatures during the operation of the engines. Hence, the effect of strain rates and temperatures is also considered. The compression tests are carried out at different strain rates from quasi-static to dynamic viz., 3*10-4 to 102/s and three different temperatures RT, 100°C and 200°C. Microstructure of the alloys studied predominantly consists of eutectic colonies of α-Al and Si with a few interspersed α-Al dendrites. Modified alloy has more globular Si particles than unmodified alloy. Heat treated alloys are found to have hardening precipitates S’ & Al7Cu4Ni and 3-7 atomic layer thick zones, which may be precursors to S’ phase. A variety of large intermetallics, viz., plate like particles Al4.5FeSi, Chinese script like particles Al19Fe4MnSi2 and bulky phase Al3NiCu are also observed in the alloys. Mechanical behavior of the alloys is found to be different for different microstructures. Modification improves strength and ductility. Heat treatment improves strength of the alloy at the expense of ductility. A transition in mechanical behavior is observed after a particular strain rate for all the alloys studied. This transition strain rate is dependent on heat treatment, Si particle size and temperature. This transition can be explained on the basis of dislocation-precipitate and dislocation-Si particle interactions. Work hardening behavior of the alloys depends on the matrix microstructure in the unmodified alloys, and both matrix and particles play a role in the modified alloy. A statistically robust quantitative micro structural analysis has been carried out after compressing the samples at various strain rates and temperatures. The unique contribution of this work is the understanding of combined effect of strain rate and temperature on Si particle fracture characteristics in the alloy with different microstructures. From the fracture characteristics of Si particles, it is concluded that both dislocation pile-up mechanism and fibre loading are responsible for particle fracture in the modified alloy, whereas the fibre loading mechanism alone is sufficient to explain the particle fracture characteristics in the unmodified alloy. Si particles in the modified condition are found to cleave along the lowest surface energy planes {112} & {110} and the particles with orientations {112} & {111} are more prone to fracture. In addition to Si particle fracture, elongated Fe rich intermetallic particles are also seen to show peculiar fracture behavior. The Al4.5FeSi intermetallics with (100) as the plane of the plate cleave along (100) planes. This is a novel finding in this work and could have immense implications on the role of Fe impurities in the fracture behavior of these alloys. Moreover, since these cleavage fractures are seen to be more than 200 microns in size (which implies that the real penny shaped crack would be even larger) their role cannot be assumed to be negligible, as was previously thought. The load sharing between the Al matrix and eutectic Si particles are simulated by microstructure based finite element modeling. The program OOF (Object-Oriented Finite element analysis) is used to generate the finite element meshes for real microstructures with different Si morphology. The experimentally obtained stress – strain properties of the alloy is given as an input to describe the plastic behavior of the Al matrix, in the finite element simulation. This analysis helps to understand the effect of particle size, shape, orientation & clustering and matrix temper on the stress transferred to the Si particles. Combination of Electron Back-Scattered Diffraction (EBSD) and frequency shift, polarized micro-Raman technique is applied to validate the stress states in Si particles with {111} orientations. The stress at fracture of Si particles is also estimated from Raman technique. Even though the alloys with different microstructures show different mechanical behavior, the sequence of fracture mechanisms is found to be same for all the alloys. The failure occurs in three stages: cracking of Si particles at low strains, micro-crack formation along the fractured particles, micro-crack coalescence and propagation leading to final failure. Thus, the proposed analysis links various deformation mechanisms ranging from nano precipitate-dislocation interactions to micro short-fiber theory of load sharing by eutectic silicon along with coupled effect of strain rate and temperature. In addition, negative strain rate sensitivity is also observed in the lower strain rate regimes (3*10-4, 10-3& 102/s) at RT and 100°C for all the three alloys, and serrated flow is also observed in the same strain rate and temperature regimes. Some of the features of serrated flow can be explained by the dynamic strain aging model and some other features by precipitate shearing.

Aluminium silicon alloy has been found to be advantageous in many automobile components like pistons, cylinders, brakes and clutches. The main objective in using these alloys is to obtain lightweight and low friction at a reasonable cost without sacrificing reliability and durability. Out of all the tribological components piston skirts, piston rings and cylinder liners, have to face the most hostile of environments in an internal combustion engine. Wear mechanism of these components have been identified as abrasion, scuffing and corrosion. Narrowing down the line of interest, cylinder wear is more important than ring wear to both the engine manufacturer and the user, as cylinders are more expensive to replace than piston rings. Wear of piston ring and cylinder combination have been studied using a wide range of techniques. It is difficult to predict the tribological performance of these parts in an engine, even with the most well designed laboratory tests, due to chemical, thermal and mechanical complexities in the operating environment. Therefore, a good correlation is sought from the wear behaviour of test bed engines and laboratory tests. This should form the basis of further development particularly in terms of efficiency, weight eduction and wear life improvement of the components. Many ASTM bench-wear tests are used to study wear, some of the common tests being ball-on-disc and pin-on-disc testing. From these tests, a large database of wear information can be achieved and they offer rapid and low cost means of comparison. The only drawback is that the real components are not tested. However, since the bench tests can never simulate the engine environment completely, engine tests are always required for final verification. This thesis work reports preliminary studies of machining damage and wear in actual engine bore to set a bench mark, followed by a set of unidirectional sliding bench tests to study the wear of aluminium alloy under lubricated conditions, to classify the different wear regimes in boundary lubrication zone under different pressure conditions, and to study the effect of a surface modification technique, etching, which improves wear properties. The investigation is divided into four parts. 1. Study of subsurface damage in an actual cylinder surface as introduced by prior machining and actual worn case: A study of the microstructure of bores, processed through a range of machining variables; feed and speed, are investigated in this part of the thesis. This work suggests that the first step of rough machining may be responsible for the microstructure of the finished bore even though subsequent processing steps are intended to remove all prior damages. This also includes some observations of worn surface of an actually run engine, locating the various worn spots and studying the cause of this damage 2. Bench wear test in pin-on-disc under dry and lubricated condition with varying load and lubricant: After setting a benchmark on wear in engine using actual worn cylinder bore, a set of bench tests were carried out on aluminium alloy. Here, steel pins are slid on aluminium silicon alloy discs in the boundary lubrication regime in the presence of one drop of oil. The effect of pure hexadecane and engine oil containing additives on friction and wear are analysed and the data are discussed in terms of the formation of a mechanically mixed layer at the interface. 3. Ultra-mild Wear in Lubricated Tribology of an Aluminium Alloy: To study the different wear regimes in boundary lubrication zone, flat faces of cylindrical steel pins were slid on an eutectic aluminium silicon alloy under lubricated condition in the 1-100 MPa mean contact pressure range and 0.2 m/s sliding speed. Two transitions in wear rate were observed, at 10 MPa and 70 MPa. The wear rate in the 1-10 MPa regime was found to be very small and within the measuring instrument resolution and also insensitive to contact pressure. The regime is designated ultra-mild wear. Lack of plastic flow, minimal fragmentation of silicon particles and the presence of undistorted voids on the fractured and unfractured silicon particles in the subsurface suggest that the state of stress in the near surface region is elastic. Contact mechanical calculations demonstrate that at contact pressures less that 13.7 MPa the system is likely to shakedown to an elastic state. 4.Ball-on-disc wear tests for etched and unetched samples: In the fourth part of the thesis, comparative studies have been done between the as polished and chemically treated samples. Formation of grooves in a ball-on-disc experiment is observed on etched and unetched flats as a function of normal load and sliding distance. The groove is initially formed by plastic flow, and then expanded by micro-abrasion as the ball continues to slide on the groove. However etching causes surface hardening of the alloy, but, more importantly, creates a surface topology that reduces the peak contact pressure, which inhibits further plastic flow in the subsurface.

One of the prime challenges with age hardened Al-Cu alloys is the strength degradation at high temperatures (above ∼250°C) due to the coarsening of strengthening θ′ precipitates and associated metastable θ′ → stable θ phase transformation. A recent discovery suggests that micro-alloying with Manganese (Mn) and Zirconium (Zr) can synergistically restrict θ′ precipitate coarsening, thereby rendering an excellent high temperature stability for Al-Cu-Mn-Zr (ACMZ) alloys. The θ′ precipitates are stabilized primarily from the reduction of interfacial energy by preferential solute segregation (Mn & Zr) at θ′ precipitate/α-Al matrix interfaces. The Al-Cu-Mn-Zr alloys thereby exhibit excellent high temperature hardness and tensile properties (yield and ultimate tensile strength) in addition to superior fatigue life and creep resistance. This newly developed Al-Cu-Mn-Zr alloys also showed excellent hot tearing resistance compared to the conventional cast Al-Cu alloys so much so that it meets the industrial standards as well. These alloys also have promising manufacturing possibility by additive route. Overall, Al-Cu-Mn-Zr alloys offer great potential for the automotive industry because of their unprecedented high temperature performance which should enable engineers to build light weight passenger vehicles leading to a safer and greener environment.

<div class="section abstract"><div class="htmlview paragraph">The global automotive industry is growing rapidly in recent years and the market competition has increased drastically. There is a high demand for passenger car segment vehicles with high torque delivery and fuel economy for a pleasant drivability experience. Also, to meet the more stringent emission requirements, automakers are trying very hard to reduce the overall vehicle gross weight. In lowering both fuel consumption and CO₂ generation, serious efforts have been made to reduce the overall engine weight. An engine cylinder block is generally considered to be the heaviest part within a complete engine and block alone accounts for 3-4% of the total weight of the average vehicle, thus playing a key role in weight reduction consideration. Aluminum casting alloys as a substitute for the traditional cast iron can mean a reduction in engine block weight between 40 and 55% [<span class="xref">9</span>], even if the lower strength of aluminum compared to grey cast iron is considered. Thus, designers of aluminum engine blocks are constantly striving to design better and lighter blocks in order to improve and enhance the efficiency of automobile engines.</div><div class="htmlview paragraph">This work is a part of design and development of 2.2 L, 4-cylinder turbocharged intercooler (TCIC) diesel engine for a complete new monocoque vehicle platform, focused on automotive passenger car application with high operating in cylinder combustion pressures around 190 bar. The paper portrays the effective system approach essential for selecting aluminum as the choice of material, selection of alloy composition, casting process, heat treatment and key design criteria. The ongoing substitution of cast iron in engine blocks by aluminum casting alloys also requires the design and development of a new “tribological” system. Selection of cost-effective cylinder liner system and the drawbacks of this heterogeneous concept such as the lack of metallic bonding with the surrounding cast aluminum alloy and higher bore distortion are addressed during design and development. Statistical database, quality tools like design failure mode and effect analysis (DFMEA), design for manufacture and assembly (DFMA) etc., classical design methods, finite element analysis (FEA), advanced computer-aided engineering (CAE) and computational fluid dynamics (CFD) simulation tools have helped in materializing this concept into production. Experimental validation of the design is carried out as a part of design verification and validation. And results are elaborated to show the effectiveness of integrated approach used for the development program.</div></div>