The use of aluminium alloys in all kinds of civil engineering as the main structural material is the new trend and days goes by people are becoming more aware of how this metal combination works wonders in our daily life activities. Aluminium alloys are used widely around the world for all kinds of aeronautical requirements. The trend had started way back during zeppelin airship flights and has carried on to make inroads for modern day usability as well. This metal alloy is now also used for various forms of transportation. Mainly due to its light weight, non-corrosive characteristics and almost maintenance free use. Whether its railways, shipping or automobile the aluminium composites are now seen everywhere.
The continuous comparison with steel remains a big issue but there’s a difference between what and exactly where these are getting applied. The application factor plays a big role in deciding whether a particular structure requires steel or aluminium composite for structural modifications. There is always a debate for and against the use of aluminium alloys and their advantages are weighed against disadvantages to find a best solution. These aluminium alloy members are characterized as industrial bars or something that get affected by mechanical and imperfect geometrical fabrication units. The word allumen was used when a dubious composition is made into and dates back to Egyptian civilization.
In 1827 aluminium nugget was first obtained by Whoeler, the German chemist and it can be said that due to uncertain parentage and lots of years of gestation, the aluminium appeared as the metal of future.
Aluminium alloys which are considered as light alloys have been developed in order to increase the strength of the base metal Aluminium. Aluminium is very ductile and non-corrosive unlike steel. The Aluminium alloys need just small amount of thermic power for the production to begin. The Aluminium alloys require very small amounts of additional elements and hence are considered as a straight forward composition. These alloys mainly use comprise of magnesium, silicon, zinc copper and manganese. For any additional requirements, the use of nickel, cobalt, chromium, iron, titanium and zirconium is also found in some specific cases.
- Copper amongst of all elements is found to be one of the most important ingredients of Aluminium alloys. This is mainly because coper has appreciable solubility and strengthening effects. The strength increase with increase copper content.
- Magnesium along with copper is used to help accelerate the hardening process even at room temperature. So equilibrium compounds for this system are CuAl2 and CuMgAl2 are used which also gets into solubility during heat treatment of solution.
- The addition of silicon improves the response to artificial ageing and has specific strengthening effect. These occurs especially at higher temperatures but affects the ductility.
- Silicon added to Aluminium alloy composition has some specific effects for ageing process and also strengthening effect at higher temperatures.
- Silicon combines with this magnesium aluminium composition to form compound Mg2Si unlike the formation of other compounds like CuMgAl2, CuMg4Al6 and (Cu Fe Mn)3 Si2 Al15
- The presence of iron is beneficial as it helps in the overall strength of the alloy composition and especially at higher temperature but can also cause brittleness and hence is kept under control (Cu Fe)Al6 + Cu2FeAl7)
- Manganese addition to these Aluminium alloys helps in strengthening effect mainly because of its solubility and ability to the formation of intermediate compounds. Manganese additions remain in solution even during the casting of the alloy. The intermediates are (Cu Fe Mn)3 Si2 Al15 and (Cu Fe Mn) Al6
For all Aluminium alloy the presence of each individual elements has its own specific effects and they are mentioned as:
- The presence of magnesium helps in reducing the melting point to 451 C and also increase hardening ability during casting as well as help against salt water or sea side corrosion resistance
- Presence of silicon helps in increasing the strength as well as the ductility. The silicon in Aluminium alloy also help in reducing the melting point. The combination with magnesium allows its precipitation as well as hardening
- The presence of zinc helps in increasing the length and also allow the hot or cold precipitation followed by hardening
- Although the presence of copper helps in increasing the strength and also cold precipitation hardening but at the same time the resistance against corrosion is reduced as well. The presence also effects the weldability and ductility
- Nickel presence can increase strength under high temperature conditions but at the same time the presence affects the resistance against corrosion
- The presence of chromium increase the resistance to stress corrosion
- The presence of zirconium is considered as an stabilizing element which will influence the temperature gradient
- Apart from the presence of specific element and their respective properties we can also observe set of properties based on the casting and process of making.
- Casting alloys are usually the ones which re-melted and then casted. These are delivered in T form bars
- Wrought alloys are the ones which has to be worked hot or cold and without the re-melting process. These are commonly seen in extrusion, forging and drawing and then delivered in form of slabs, billets and rods.
Aluminium alloys can also be classified as non-heat treatable alloys or heat treatable alloys. Among the non-heat treated alloys like AlMn, AlMnMg and AlMg the strength can be increased by cold working. The heat treated alloys are AlMgSi, or AlZnMgCu and or AlCuMg and involves higher strength in heat affected zone and can be separated only by tempering with water or air, ageing at room temperature or can be heated up to 450 or 350 degree centigrade.
There are various forms of alloys and these are classified on a variety of count. The nature of bonding, temperature required to create the bond the specific need of the product.
It’s a mix of copper, zinc, magnesium and to an extent nickel as well. Its main application to make forged pistons, various general purpose and aerospace.
This coded aluminium alloy consists of Copper, zinc, magnesium, manganese and silicon. The main applications are marine based applications.
This alloy consist of copper, magnesium and nickel and the application is for making piston.
The alloy consists of copper, zinc, magnesium manganese and silicon. The main application is used as good shock absorber.
Aluminium and copper form the CuAl2 which dissolves completely in liquid aluminium. When this is quenched and the aged artificially a very hard alloy is obtained. The CuAl2 which doesn’t go through ageing do not precipitate and hence is found to be unstable. The ageing actually yields the fine particles of CuAl2 which then provides the strength to the alloy.
Other alloys are
- AA-8000 used for all kinds of wiring inside building
- Alnico or the combination of Aluminium, nickel and coper
- Magnalium which has 95% of Al and 5% of magnesium
- Nambe, which has the main metal aluminium and 07 other elements in combination
- The combination of magnesium oxide and aluminium is termed as Magnox
Aluminium alloys are either segregated either by the fabrication process, where casting alloys and wrought alloys are considered and treatment with heat to understand whether it’s a heat treatment alloy or non-heat treated alloy or by their composition and elemental percentages. There are certain coding that goes into identifying the aluminium purity and composition etc.
1xxxx is for pure aluminium, which is found to be more than 99% pure, 2xxx is for copper doping, 3xxx is for manganese doping and so on. If it is equal to zero then the impurities are uncontrolled and can vary between 1 and 9 depending upon the limits of impurity. The numerical designation for aluminium alloy was used first by aluminium association for wrought alloy and now it is used worldwide.
For all kinds of wrought alloys just one or two figures are taken while the letter N is placed before two figures to signify the cold worked alloy. The letter H is placed before the two figures for heat treatment alloy. When LM is used that signifies the presence of casting alloys.
For all kinds of non-ferrous alloys, the aluminium alloys are considered the most important due to their wide range of properties and an apt substituent for iron although costly. The excellent set of properties of this set of alloys of aluminium makes it the most ideal material for all kinds of future fabrications.
- The aluminium alloys have near perfect thermal conductivity
- The aluminium alloys have excellent electrical conductivity though less than pure copper or rest of inert metals.
- The aluminium alloys have low mass density which makes it the ideal material for making fabricating materials light weight
- These aluminium alloys have low melting point
- The aluminium alloys have very slow corrosive effect or near perfect corrosion resistance. Although aluminium has natural affinity towards oxygen but the oxide of aluminium itself helps in protecting the outer layer from further corrosion
- The aluminium alloys are non-toxic in nature and hence safe to use
- The aluminium alloys have highest reflective property which makes it ideal for external covering
- The aluminium alloys have low emission level which makes it again a chosen material for fabrications inside the house
- The aluminium alloys have ductile property and soft as well making it ideal for all kinds of interior designing
The overall application of alumnium metal has been truly based on how good the doping or alloying with other metals were carried out which not only enhanced the life but also made it an ideal companion of new age fabrications.