Extract from “Newsletter of Aluminium Fabrication Industry & Market”
Lightweight Development
Aluminium (2.7g/cm3) weights less than half of steel (7.6/cm3) and copper (8.5g/cm3). The potential merits of aluminium as a kind of lightweight material are obvious. This is of course simply a basic comparison in theory. In practice, automotive manufacturers have to take into consideration a number of factors in relation to the respective design and function when choosing suitable materials for different auto parts. Those considerations are based on functional performances such as mechanical strengths, stiffness and weight.
The application of aluminium in the transportation sector reduces the weight of a vehicle, improves fuel efficiency and lowers emissions of greenhouse gases simultaneously. While using lightweight materials contributes to weight reduction, certain processing technologies applied on parts and components can further reduce the weight of vehicle bodies. For instance, relatively complex porous aluminium extrusion parts or high-strength thin-walled vacuum aluminium die-cast pipes are new designs that have enormous room for further development.
In 1994, Audi was presented with a difficult choice of materials when designing the A8 model. It had to choose between building a steel-made model which weighted 441kg, and using aluminium as a substitute to build a model which weighted only 247kg. Once aluminium was chosen as the material for the vehicle body of the A8 model, other additional weight reduction means were also taken into consideration. For example, a more compact engine or fuel tank was needed to meet certain performance requirements (acceleration, fuel mileage consumption). According to Audi, those indirect weight reduction means shed 45kg off the vehicle, which was equivalent to about 23% of the 194kg direct weight reduced by the aluminium car body. In other words, the overall vehicle weight was lowered to 239kg because of the use an aluminium-made car body. A research in vehicle weight reduction indicates that indirect weight reduction can be as high as 50%-100% of the direct weight reduction.
Safety
Lightweight materials when combined with superior designs can lower the number of injuries and safe lives in case of an accident. Safety has always been the first priority of both manufacturers and customers in designing and purchasing a vehicle. It is of paramount importance for a vehicle to provide protection to both the driver and its passengers and minimize injuries to any other parties in case of an accident.
Aluminium is a perfect choice to satisfy the abovementioned objectives. It does not merely reduce the vehicle weight but also enhances its performance. The mechanical properties of aluminium alloy make possible a vehicle that offers high strength, excellent shock absorption and low running cost. In order to provide the best protection to passengers in case of an accident, a firm and stable passenger compartment is designed as a cushion to absorb shock. The shock absorption capacity of aluminium is twice of low-carbon steel. Aluminium also has advantages over newly developed high-strength steel items. Compared to steel, aluminium parts offer higher stiffness for two reasons. First, aluminium-made parts are thicker (to perform the same function, aluminium parts are usually 50% thicker than their steel counterparts). The second reason is that the elimination of welded joints by combining closed-end aluminium extrusion technology and good designs makes the parts even stronger. As a result, the strength of the auto parts could be increased even on a 40-50% weight reduction.
Aluminium satisfies relevant requirements such as excellent shock absorption ability, good protection to passengers, and low maintenance costs, to name but a few benefits. Examples of aluminium-intensive vehicle models with superior safety performance are the Audi A8 model which uses large aluminium die-cast and extrusion parts as the body frame, and the Jaguar XJ model which uses large amount of aluminium sheet in its car body. A more representative example is the application of aluminium in vehicles of mixed material design. Aluminium has been widely applied in lightweight crash management systems. For instance, in the design of steel mixed vehicles, aluminium-made parts are used in the front and rear bumpers, crash boxes and side impact protection system etc.
Diversification
In the design of lightweight, low-cost, efficient vehicle structure, the biggest advantage of aluminum is its malleability. It could be applied in sophisticated dashboard through a variety of processing technologies from high efficiency stamping to processing technologies to manufacture a small number of products at relatively low cost. Aluminium can be turned into different complicated shapes of different thickness, open or closed aluminium extrusion parts. Different technologies such as forging and casting could be applied, depending on the requirements.
With different casting and processing technologies, the size, shapes and functions of die-cast aluminum products will also be different. Not only can extrusion or subsequently processed aluminium parts or high-quality thin-walled aluminum die-cast parts be used to increase the load bearing capacity, but they can also be used as connecting parts. As such, through the proper application of these processed materials, new revolutionary solutions can be developed thereby reducing weight and saving cost at to a great extent.
Aluminium alloy parts have more advantages. For example, it is widely used in the transportation industry because of its good conductivity for heat and electricity transmission and therefore its application in heat radiators, internal combustion engines and motors are common. Highly versatile assembly is another key factor for aluminum to have wide application in the transportation sector. Assembly works, includes welding and joining of different parts (stamping plates, castings, processed extrusions, forging parts, etc.) made of a range of materials such as aluminium and steel, magnesium, plastic and synthetic materials.
Economical
Aluminium-intensive vehicles are economical and cost effective as they reduce fuel consumption. Automotive manufacturers use aluminium for weight reduction. Their focus switch from system cost analysis to life-cycle cost analysis so as to improve driving performance and reduce both fuel comsumption and pollutant emissions. The automotive industry is also considering ways to achieve weight reduction in either one or multiple auto parts. They will then seek other opportunities to further reduce weight and costs of other components for other automobiles. Studies have shown that cost effective solutions are found in the bodies of aluminium-intensive passenger cars and trucks. Under certain conditions, it is feasible for large capacity vehicle to use aluminium-intensive vehicle. The aluminium-intensive automobile can save fuel consumption to a greater extent and that will finally bring great and real benefits to ultimate users. For example, the fuel consumption cost of the new Jaguar XJ Model (Jaguar XJ), by using the lightweight aluminium body structure, is pretty low compared to other similar steel structure models. Furthermore, the aluminium has a relatively high scrap value and thus playing an important role in subsidizing processing works for old and scrap automobile.
Recyclability
Aluminium can be used repeatedly. This can save 95% of energy generate from the production of primary aluminium products. Aluminium has been a key material in the recycling system of the transportation sector. It can be used in almost any field, lower the emissions of pollutants and save energy as well. Currently, recycled aluminium plays an important role in the old and scrap automobile processing works for its relative high scrap value. As at April 2010, aluminium automobile waste recorded US$1830/ton in the US Consumer Price Index while the price of scrap steel automobile is just US$400/ton.
The increasing use of aluminium adds value to the automobile and also increases its scrap value at the same time. It greatly reduces the need to bury non-metallic waste in US. A large number of efficient processing techniques are used in handling the aluminium recycling scrap automobiles. Some separation techniques are being used or developed to further improve recycling percentage and quality of the recycling material.
Scrap aluminium, which are sorted out by different separation technologies, are mainly processed into cast aluminium alloys. Those are used to produce castings including engine covers, cylinder head and transmission box. Nowadays, more and more forged aluminium alloys have been used in the car body. The deformed alloy scrap parts will increase continually. Therefore, in the next few decades, from an economic point of view, it is feasible to collect deformed alloy separated from the cars.
Trendiness
In the past 200 years, the global trend is to create extra mobility through innovative transportation means.. Exemplary products under this trend are automobiles which is a perfect combination of superb design and high quality materials. Over the past two centuries, certain trendy automobiles models (also include building architecture, consumer products and fashionable accessories) use aluminium not only for functional purpose but also because of the aesthetic effect it creates. Its durability, malleability and diverse application after processing are also taken into consideration. Ford’s air trailers, London’s Eros, Phillippe Starck’s 1006 chair, iPod and BMW 328 racing automobiles have fully utilized the properties of lightweight, ultra strength and high durability of aluminium. Meanwhile, aluminium is also used to satisfy the functional goals and to offer the unique cultural experience through their trendy outlooks and feelings.
Aluminium has a number of properties that differentiate it from other metals. It is clean, smooth, flat, innovative and highly versatile that it can be casted and extruded into a wide array of products. An article in the Aluminum News-Letter reported that “when an engineer designs the shape of the extrusion parts, their designs are not only placed on the structure of the traditional shape of the parts. In fact, they design the shape that can suit the structure according to its framework.” More importantly, the lightweight property of aluminium can bring a faster moving speed.
Entering the era of aviation, aluminium is a material with a futuristic touch. It combines appealing outlook with high functionality to shape the contemporary transportation development trend. Aluminium has been a preferred material for sea, air and land transportation not merely because of its lightweight, but also attributable to the attractive outlook that it creates.
Durability
Even without painting and coating, aluminum can resist external corrosion, thus eliminating certain electrochemical processing, coating and painting required for some of the competing materials. No matter it is in a heated desert, exposed to severe coldness in the North Pole or placed under sunlight for prolonged hours, aluminium will not be easily weakened, nor will its strength be lessened. With proper designs and under suitable production conditions, aluminium components and structural parts showed high corrosion resistance. As a result, aluminium has become the first choice for the transportation industry. In fact, aluminium is a highly reactive metal that can be oxidized quickly in air. This forms a transparent oxidized protective aluminium layer to prevent it from further intrusion of oxygen and other gases or liquids. The protective layer is attached to the surface of the alumnium and will not fall off so that it can prevent exposure to more sides of oxidation. Once the protective layer is destroyed, it will form another one automatically to maintain an on-going protection.
Corrosion can be prevented by following some guidelines when applying the material in the transportation industry. For example, when two different types of metals are in direct contact in an electrolyte solution such as water, there will be corrosion. A common corrosion is found between the connecting area between steel and aluminium parts. A major precautionary measure is to place an insulation layer to separate the aluminium and steel parts to avoid direct contact.
