Input
Aluminium is one of the most abundant elements on Earth. Aluminium is obtained from bauxite, which is an aluminium ore, which is purified to get a white powder called aluminium oxide. The process of refining bauxite to alumina is known as bayer process. From aluminium oxide, aluminium is extracted. But in terms of energy, the amount of energy required to extract aluminium is significantly high. The reason is that the strength of chemical bonds between aluminium and oxygen is considerably strong. Therefore, significantly large energy is required to separate the bond. Electrolysis process mainly does the extraction process.
Regarding cost, the process of extraction is very expensive. The extraction process involves removal of all topsoil, vegetation and soil beneath. This process requires hours of work with a large number of workforce and expensive machinery. Apart from extraction, the land itself costs in millions. And to transport the ore from the land site to refinery unit will also be expensive.
Aluminium offers lightweight which makes their application in automotive industry. But the pure aluminium cannot be used as it lacks tensile strength. However, alloying aluminium with elements such as magnesium, copper, silicon and manganese can improve the strength properties and tailor the materials to specific applications. At present, the usage of aluminium has been increased from 110 kg in 1995 to 250 kg or 340 kg in 2015, i.e., 80% usage has shown in the automotive industry. The aluminium alloys has been used in the form of wrought and cast in automotive industry. The availability, cost and the energy needed for the elements to form aluminium alloy are easy. The type of the alloy varies with the type of application required in automotive industry. The alloy series are divided into eight categories based on the first digit of the assigned name. The first digit (Xxxx) is used to describe the aluminium alloy series and will also indicate the principal alloying element added to the aluminium alloy. The second single digit (xXxx) shows the number of modification made to the specific alloy, and the third and fourth digits (xxXX) are numbers used to identify the particular alloy within the series.
Output
In the past, various measures were taken to reduce the consumption of fuel by the automotive vehicle. Weight reduction in the automotive was considered as the most effective way of reducing the fuel consumption. In the traditional method, this was achieved by decreasing the steel sheet thickness for body panels by increasing the strength of the steel. But this approach was limited as panel stiffness would eventually decrease. For this reason, aluminium alloys have been used in the industry. It is approximately one-third the weight of steel. Right now, the use of aluminium alloy has not only been used as engine blocks but also for hoods, trunk lids and body panels.
Use of aluminium alloys offered a significant improvement in the properties such as thermal, mechanical, corrosion resistance, formability and weldability. However, all these properties cannot be obtained from one single alloy series. Each series have their unique properties and purposes to be used in automotive for a specific application.
For instance, 1xxx series has 99% pure aluminium which have high corrosion resistance, thermal and electrical properties but are low in mechanical properties. Whereas, 2xxx series with copper as the principle element have high strength and fatigue resistance but do not have excellent corrosion resistance when compared to other series.
End-of-Life
Aluminium can be recycled which in turn reduces the energy needed to extract the bauxite for the production of primary aluminium. It has been reported that around 33% of the world supply of aluminium is used at present and is expected to rise to 40% by 2025. Secondary aluminium is usually produced from scrap metals, it is either new scrap from the production and manufacturing or the old scrap from the recycled aluminium. The energy needed for recycling aluminium is only 5% of that required for the production of primary aluminium. The only energy required is heat and melt, which is very minimal compared to extraction method.
Regarding cost, there is no cost involved in the transportation compared to extraction, i.e., transfer of the ore from land site to refinery unit. The equipment required for recycling aluminium is immensely less. And this not only saves energy and cost but also decreases the effect on the environment.