File Name: structure and properties of aluminium and its alloys .zip
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- Chemical Composition and Properties of Aluminum Alloys
- Structure and properties of aluminium–magnesium casting alloys after heat treatment
- Introductory Chapter: Structural Aluminum Alloys and Composites
Since the forming of the microstructure depends on the specific of the casting method, which directly affects further mechanical and physical properties of the material, it is important to understand how to control the microstructure of the cast to understand changes that taking place during the crystallisation process. For estimating the metallurgical quality of the liquid metal before casting, the thermal-derivative analysis TDA is utilised. The TDA has been used for a long time, in both ferrous and non-ferrous industries casting.
With the growth of aluminum within the welding fabrication industry, and its acceptance as an excellent alternative to steel for many applications, there are increasing requirements for those involved with developing aluminum projects to become more familiar with this group of materials. The wrought and cast aluminums have different systems of identification. The wrought system is a 4-digit system and the castings having a 3-digit and 1-decimal place system. Wrought Alloy Designation System - We shall first consider the 4-digit wrought aluminum alloy identification system. The first digit X xxx indicates the principal alloying element, which has been added to the aluminum alloy and is often used to describe the aluminum alloy series, i.
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Aluminium alloys or aluminum alloys ; see spelling differences are alloys in which aluminium Al is the predominant metal. The typical alloying elements are copper , magnesium , manganese , silicon , tin and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable.
Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al—Si , where the high levels of silicon 4. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.
Alloys composed mostly of aluminium have been very important in aerospace manufacturing since the introduction of metal-skinned aircraft. Aluminium-magnesium alloys are both lighter than other aluminium alloys and much less flammable than other alloys that contain a very high percentage of magnesium.
In a wet environment, galvanic corrosion can occur when an aluminium alloy is placed in electrical contact with other metals with more positive corrosion potentials than aluminium, and an electrolyte is present that allows ion exchange. Referred to as dissimilar-metal corrosion, this process can occur as exfoliation or as intergranular corrosion. Aluminium alloys can be improperly heat treated.
This causes internal element separation, and the metal then corrodes from the inside out. Aluminium alloy compositions are registered with The Aluminum Association. Many organizations publish more specific standards for the manufacture of aluminium alloy, including the Society of Automotive Engineers standards organization, specifically its aerospace standards subgroups,  and ASTM International.
Aluminium alloys with a wide range of properties are used in engineering structures. Selecting the right alloy for a given application entails considerations of its tensile strength , density , ductility , formability, workability, weldability , and corrosion resistance, to name a few. A brief historical overview of alloys and manufacturing technologies is given in Ref. On the other hand, pure aluminium metal is much too soft for such uses, and it does not have the high tensile strength that is needed for airplanes and helicopters.
Aluminium alloys typically have an elastic modulus of about 70 GPa , which is about one-third of the elastic modulus of steel alloys. Therefore, for a given load, a component or unit made of an aluminium alloy will experience a greater deformation in the elastic regime than a steel part of identical size and shape. With completely new metal products, the design choices are often governed by the choice of manufacturing technology. Extrusions are particularly important in this regard, owing to the ease with which aluminium alloys, particularly the Al—Mg—Si series, can be extruded to form complex profiles.
In general, stiffer and lighter designs can be achieved with Aluminium alloy than is feasible with steels. For instance, consider the bending of a thin-walled tube: the second moment of area is inversely related to the stress in the tube wall, i. For this reason, bicycle frames made of aluminium alloys make use of larger tube diameters than steel or titanium in order to yield the desired stiffness and strength. In automotive engineering, cars made of aluminium alloys employ space frames made of extruded profiles to ensure rigidity.
This represents a radical change from the common approach for current steel car design, which depend on the body shells for stiffness, known as unibody design. Aluminium alloys are widely used in automotive engines, particularly in cylinder blocks and crankcases due to the weight savings that are possible.
Since aluminium alloys are susceptible to warping at elevated temperatures, the cooling system of such engines is critical. Manufacturing techniques and metallurgical advancements have also been instrumental for the successful application in automotive engines. In the s, the aluminium cylinder heads of the Corvair earned a reputation for failure and stripping of threads , which is not seen in current aluminium cylinder heads.
An important structural limitation of aluminium alloys is their lower fatigue strength compared to steel.
In controlled laboratory conditions, steels display a fatigue limit , which is the stress amplitude below which no failures occur — the metal does not continue to weaken with extended stress cycles.
Aluminium alloys do not have this lower fatigue limit and will continue to weaken with continued stress cycles. Aluminium alloys are therefore sparsely used in parts that require high fatigue strength in the high cycle regime more than 10 7 stress cycles. Often, the metal's sensitivity to heat must also be considered.
Even a relatively routine workshop procedure involving heating is complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used can reverse or remove heat treating, therefore is not advised whatsoever. No visual signs reveal how the material is internally damaged. Much like welding heat treated, high strength link chain, all strength is now lost by heat of the torch. The chain is dangerous and must be discarded.
Aluminium is subject to internal stresses and strains. Sometimes years later, as is the tendency of improperly welded aluminium bicycle frames to gradually twist out of alignment from the stresses of the welding process. Thus, the aerospace industry avoids heat altogether by joining parts with rivets of like metal composition, other fasteners, or adhesives. Stresses in overheated aluminium can be relieved by heat-treating the parts in an oven and gradually cooling it—in effect annealing the stresses.
Yet these parts may still become distorted, so that heat-treating of welded bicycle frames, for instance, can result in a significant fraction becoming misaligned. If the misalignment is not too severe, the cooled parts may be bent into alignment. Of course, if the frame is properly designed for rigidity see above , that bending will require enormous force. Aluminium's intolerance to high temperatures has not precluded its use in rocketry; even for use in constructing combustion chambers where gases can reach K.
The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable, lightweight component.
Because of its high conductivity and relatively low price compared with copper in the s, aluminium was introduced at that time for household electrical wiring in North America, even though many fixtures had not been designed to accept aluminium wire. But the new use brought some problems:. All of this resulted in overheated and loose connections, and this in turn resulted in some fires. Builders then became wary of using the wire, and many jurisdictions outlawed its use in very small sizes, in new construction.
Yet newer fixtures eventually were introduced with connections designed to avoid loosening and overheating. Another way to forestall the heating problem is to crimp the short " pigtail " of copper wire.
A properly done high-pressure crimp by the proper tool is tight enough to reduce any thermal expansion of the aluminium. Today, new alloys, designs, and methods are used for aluminium wiring in combination with aluminium terminations. Wrought and cast aluminium alloys use different identification systems. Wrought aluminium is identified with a four digit number which identifies the alloying elements.
Cast aluminium alloys use a four to five digit number with a decimal point. The digit in the hundreds place indicates the alloying elements, while the digit after the decimal point indicates the form cast shape or ingot. The temper designation follows the cast or wrought designation number with a dash, a letter, and potentially a one to three digit number, e. The definitions for the tempers are:  .
Note: -W is a relatively soft intermediary designation that applies after heat treat and before aging is completed. The -W condition can be extended at extremely low temperatures but not indefinitely and depending on the material will typically last no longer than 15 minutes at ambient temperatures.
The International Alloy Designation System is the most widely accepted naming scheme for wrought alloys. Each alloy is given a four-digit number, where the first digit indicates the major alloying elements, the second — if different from 0 — indicates a variation of the alloy, and the third and fourth digits identify the specific alloy in the series. For example, in alloy , the number 3 indicates the alloy is in the manganese series, 1 indicates the first modification of alloy , and finally 05 identifies it in the series.
The Aluminum Association AA has adopted a nomenclature similar to that of wrought alloys. British Standard and DIN have different designations. In the AA system, the second two digits reveal the minimum percentage of aluminium, e. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively. The addition of scandium to aluminium creates nanoscale Al 3 Sc precipitates which limit the excessive grain growth that occurs in the heat-affected zone of welded aluminium components.
This has two beneficial effects: the precipitated Al 3 Sc forms smaller crystals than are formed in other aluminium alloys  and the width of precipitate-free zones that normally exist at the grain boundaries of age-hardenable aluminium alloys is reduced. In principle, aluminium alloys strengthened with additions of scandium are very similar to traditional nickel-base superalloys , in that both are strengthened by coherent, coarsening resistant precipitates with an ordered L1 2 structure.
However, Al-Sc alloys contain a much lower volume fraction of precipitates and the inter-precipitate distance is much smaller than in their nickel-base counterparts.
In both cases however, the coarsening resistant precipitates allow the alloys to retain their strength at high temperatures. The increased operating temperature of Al-Sc alloys has significant implications for energy efficient applications, particularly in the automotive industry. Replacement of these materials with lighter aluminium alloys leads to weight reductions which in turn leads to increased fuel efficiencies.
This is achieved by the formation of a slow-diffusing zirconium-rich shell around scandium and erbium-rich precipitate cores, forming strengthening precipitates with composition Al 3 Sc,Zr,Er.
Titanium alloys , which are stronger but heavier than Al-Sc alloys, are still much more widely used. The main application of metallic scandium by weight is in aluminium-scandium alloys for minor aerospace industry components.
These alloys contain between 0. They were used in the Russian military aircraft Mig 21 and Mig Some items of sports equipment, which rely on high performance materials, have been made with scandium-aluminium alloys, including baseball bats ,  lacrosse sticks, as well as bicycle  frames and components, and tent poles.
Due to its light-weight and high strength, aluminium alloys are desired materials to be applied in spacecraft, satellites and other components to be deployed in space. However, this application is limited by the energetic particle irradiation emitted by the Sun. The impact and deposition of solar energetic particles within the microstructure of conventional aluminium alloys can induce the dissolution of most common hardening phases, leading to softening.
The recently introduced crossover aluminium alloys   are being tested as a surrogate to 6xxx and 7xxx series in environments where energetic particle irradiation is a major concern. Such crossover aluminium alloys can be hardened via precipitation of a chemical complex phase known as T-phase in which the radiation resistance has been proved to be superior than other hardening phases of conventional aluminium alloys alloys.
The following aluminium alloys are commonly used in aircraft and other aerospace structures:  . Note that the term aircraft aluminium or aerospace aluminium usually refers to As filler, aluminium alloy strips can be combined to intricate applications to bond two metals. These distinctive features make aluminium alloy one of the preferred alloys for heat transfer and heat exchangers manufactured for aerospace applications.
They are regularly used as architectural and structural members. The following list of aluminium alloys are currently produced, [ citation needed ] but less widely [ citation needed ] used:. These alloys are used for boat building and shipbuilding, and other marine and salt-water sensitive shore applications. These alloys are used for cycling frames and components [ citation needed ].
Chemical Composition and Properties of Aluminum Alloys
Aluminium alloys or aluminum alloys ; see spelling differences are alloys in which aluminium Al is the predominant metal. The typical alloying elements are copper , magnesium , manganese , silicon , tin and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al—Si , where the high levels of silicon 4. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.
When beginning any project, material selection is one of the most fundamental choices that can dictate its success. Airplanes, computers, buildings, and other modern technologies all use specialized materials that allow them to complete amazing tasks, and one of the most important materials in this regard is the metal aluminum. Aluminum is the most abundant metal on Earth, making it an attractive, cost-effective option for builders when considering metal for their project. This alloying process has allowed many grades of aluminum alloys to be produced, and there are so many grades that the Aluminum Association has classified these types of aluminum into categories based on alloying elements and material properties. This article will give a brief introduction to the different types of aluminum, how they differ, and which alloys are best suited for certain applications.
Lightness is an essential property of aluminium. The electrical conductivity of When exposed to air, a layer of aluminum oxide forms almost instantaneously on the surface of the aluminum. This layer has excellent resistance to corrosion. It is fairly resistant to most acids but less resistant to alkalis. A luminium was first isolated by Oersted and produced chemically as small ingots by Sainte-Claire Deville in France in At that time, aluminium was more expensive than gold but attracted the attention of Napoleon III who foresaw its use for military purposes such as lightweight body armour.
Structure and properties of aluminium–magnesium casting alloys after heat treatment
The versatility of aluminium makes it the most widely used metal after steel. Although aluminium compounds have been used for thousands of years, aluminium metal was first produced around years ago. In the years since the first industrial quantities of aluminium were produced, worldwide demand for aluminium has grown to around 29 million tons per year. About 22 million tons is new aluminium and 7 million tons is recycled aluminium scrap.
The data contained on this website has been compiled by United Aluminum. The data should be thoroughly evaluated and tested by technically skilled personnel before any use is made thereof. United Aluminum assumes no responsibility or liability for any use of this data and no warranties are given or implied by United Aluminum. By accessing this Website or any pages herein, you indicate that you have read this Agreement, understand it, and agree to be bound by its Terms and Conditions.
Allotropes Some elements exist in several different structural forms, called allotropes. Each allotrope has different physical properties. For more information on the Visual Elements image see the Uses and properties section below. Group A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.
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Introductory Chapter: Structural Aluminum Alloys and Composites
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