ieep 2012 vujadinovic_karadzic

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USE OF ALUMINIUM IN THE PRODUCTION OF CARS

Radoje Vujadinovi, Uro Karadi

University of Montenegro, Faculty of Mechanical Engineering, Dorda Vaingtona bb,

81000 Podgorica, Crna Gora

Resume: In order to solve ecological problems caused by the emissions of exhaust gasses from cars, one

of ways is the use of aluminium in a car industry. By the use of aluminium in the manufacturing of cars,

the lighter structure is obtained which results in a smaller fuel consumption and, therefore, smaller

emission of exhaust gasses. Beside the ecological improvement, a better security of cars in case of

collision is achieved by the use of aluminium in the production of cars, and better driving characteristics

are visible and they are mirrored in the improvement of acceleration and shortening the trace of braking.

The characteristics of aluminium and its alloys that found their use in a car industry are presented in this

paper. The commercially-technological aspects of prospects of use of some aluminum alloy types are alsopresented.

1. INTRODUCTION

More and more pronounced ecological problems on the Earth planet to which cars significantly contribute

forced the leading world economies to set significantly more rigorous standards for car manufacturers

related to the gas emissions from cars which they produce. The strategy aiming to achieve smaller engine

sizes and, therefore, the reduction of fuel consumption and the emission of dangerous gasses is called

downsizing. The downsizing of engine sizes also leads to the decreasing a chassis and all its parts. Beside

an engine size, a car mass can also be reduced by the decrease of a chassis mass and some car

components (seats, car interior...). This is achieved by the replacement of some steel parts with

aluminium alloys, and also by the use of various composite materials and plastics in the manufacturing

process of other car components. Modern cars with chassis parts made of aluminium alloys can be lighter

up to 24% and the fuel consumption is smaller up to 2L by 100 km.

The reduction of a car weight leads to the reduction of fuel consumption meaning the reduction of exhaust

gasses. The car weight reduction of 10% has an average fuel saving of about 8% as a consequence. In

cars, each kilogram of inbuilt aluminium replaces in average about 2 kilograms of steel.

The basic concepts of car safety are based on the idea that the impact energy in a collision be absorbed by

a chassis and by passengers and to prevent the penetration of some parts of a car into passenger cabin.

The very fact that by the replacement of a steel kilogram with an aluminium kilogram gives two or more

times stronger structure indicates the possibilities of installation of additional construction elements for

the increase of safety and that this still stays in the area of a reduced car weight. Also, aluminium can

approximately absorb two times more of an impact energy than steel. Namely, aluminium elements which

are designed in such a way that during a collision behave in previously defined manner, i.e. which absorb

a high part of an impact energy in all circumstances, can be inbuilt.

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The introduction of aluminium structures enabled the introduction of new constructional solutions that

have essentially improved driving characteristics. First of all, this had been used and developed for race

cars, and many similar solutions are visible in passenger cars or various trucks. First of all, here emerge

improved characteristics of stiffness, vibration reduction, noise etc. The weight reduction directly

influences the acceleration rise and the shortening of braking trace.

2. CHARACTERISTICS OF ALUMINIUM

Aluminium is third most present element in the earth crust, behind oxygen and silica(8.07%). Pure

aluminium is soft and of limited strength. By the alloying with Cu, Mg, Si, Mn and Zn, it attains the

characteristic that makes it convenient for use in many industrial branches. Aluminium belongs to the

group of light metals (specific mass 2.7 g/cm 3) and belongs to the group of low-strength materials-soft,

flexible. The melting temperature of aluminium is 660C. It has a high electrical and heat conductivity. It

also has a high corrosion resistance because a homogenous layer of aluminium oxide is formed what

protects aluminium from further influences.

The characteristics of technically pure aluminium in annealing state are, conventional flow stress Rp0,=24

N/mm2, tensile strength Rm=69 N/mm2, elongation A5,65=42%, hardness HBS=19 and elasticity module

E=70000 N/mm2. Cold deformed aluminium (deformation degree75%) has an increased hardness but also

reduced flexibility: Rp02=124 N/mm2, tensile strength Rm=13 N/mm

2, elongation A5,65=6%, hardness

HBS=35.

Aluminium alloys are most frequently used in the industry, and depending on hardness (admixture Fe,

Cu, Zn, Si and other metals), there are several kinds of aluminium Al 99.80 where admixtures occupy

0.2%, and 99.7, 99.5 where the admixtures occupy 0.03 and 0.05% respectively. Aluminium can be

alloyed with a bigger number of elements. Mn, Mg, Si, Cu and Zn.

Figure 1. Protective oxide aluminium layer

The resistance to corrosion of aluminium is achieved by forming of protective oxide layer Al 2O3 at an

ambient temperature. This layer reaches the depth of 0.1 m (anodising 10 m). This oxide makes Al

stabile in the air and sea water. The cleaner aluminium the higher resistance to corrosion. However, it

does not resist neither to hydroxides (NaOH, KOH) nor to acids of halogen elements (HCl, HF).

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As has already been mentioned, aluminium can be alloyed with a bigger number of elements Mn, Mg, Si,

Cu and Zn and all the alloys can be divided into two basic groups: aluminium alloys for the plastic

processing and alloys for casting. There are subgroupsalloys that are not thermally processed

(strengthening by dissolution, deforming and dispersion), alloys that are thermally processed

(strengthening by thermal precipitation). They can be divided according to the number of added elements

into double, triple and complex.

Figure 2: Aluminium alloys

Aluminium alloys for processing by deforming- Most frequent alloying element for these alloys are Mn,

Mg, Cu, Zn and Ni.

Manganese (Mn) increases a strength, machine ability by deforming, recrystallisation temperature,

resistance to corrosion and limits grain rise in solution during solution annealing.

Magnesium (Mg) increases power and resistance to corrosion.

Cuprum (Cu) and Zinc (Zn) strengthens the alloy but deteriorates the machinability by a deforming and

resistance to corrosion.

Nickel(Ni) positively affects mechanical properties, especially at higher temperatures and resistance to

corrosion.

3. TYPES OF ALUMINIUM ALLOYS THAT ARE USED FOR PRODUCTION OF AUTO

CHASSIS PARTS

In the history of use of Al alloys for the fabrication of some parts or entire chassis, in majority of car

producers both in America and Europe, during the initial developmental phase, alloys 2036 based on Cu

and 5182 based on Magnesium had a dominant role. By the use of these alloys, the demanded stiffness of

a chassis was achieved by the embedding of sheet metal with an increased thickness in relation to the

steel in a range of 20% to 40%. Alloy 2036 which is prone to aging ( strengthens by aging) was used for

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the fabrication of external chassis elements , while the alloy 5182, because of characteristic surface

texture due to Lunders deformation, was more directed to the fabrication of internal chassis parts. By the

comparison with the alloy 2036, the alloy 5182 strengthens by a cold deformation and effect of

dissolution strengthening mechanism. One important difference in behavior during the baking of a

coloured chassis stems from this difference. Namely, at a higher temperature on which the baking is

executed (around 200 C), hardness of AlMg alloys decreases, and, for 2036, due to precipitationstrengthening, fairly bigger hardness can be achieved. However, the combination of mentioned alloys is

very inconvenient from the standpoint of secondary treatment in sense of a waste due to cuprum present

in an alloy 2036. In searching for an alloy which would be compatible in waste with the 5000 series, the

alloys from the family 6000 based on AlMgSi were selected. The alloys from this series are also

characteristic by the absence of Lunders deformation, high strength after aging and by good weld ability.

Main disadvantages are small ductility (possibility of shaping) and the occurrence of a specific surface

with reefs parallel to the rolling direction due to a specific texture.

4. COMMERCIALY-TECHNOLOGICAL ASPECTS OF PROSPECTS OF USE OF

ALUMINUM ALLOY TYPES

In USA, the researching-commercial producer association was formed during 1990s (three companies

which produce rolled products: ARCO (Aluminium Inc. Century Aluminium and Commonwealth

Aluminium), users (Ford Motor Company established a group USAMP-American partnership for car

materials) and certain governmental expert groups (Department of Ministry for Energy USA, American

engineer association, research centre and development of technologies etc.), under the name ALCARTM

(1) , which needed to estimate the prospects of needs for aluminium sheet metal in car chassis.

After the comprehensive analyse based on a mark of leading commercial-expert institution, the mentioned

group derived the following conclusions:

a) Future needs in sense of making car chassis lighter will be in a continual rise.

b) Thermally machineable alloys of 6000 series are superior in sense of mechanical properties and

the quality of surface. However, their production is much more demandingit is necessary to have

a modern equipment and technology for a continual thermal processing which is these days

available only to big companies that essentially influence the final price.

c) The expert analyses of costs of thermally machineable (6000) and thermally non-machineable

alloys (5000) taking into account all the elements of quality, showed that investment costs and

variable costs of production, AL-Mg alloys form 6000 series should be at least 10% cheaper than

alloys of 6000 series.

d) The difference in the price of material in favour of Al-Mg alloys will enable fast and more

prevalent use of aluminium in car structures.

The successful use of alloys from 5000 series instead of alloys from 6000 series can be expected in the

area of structural car components, internal and external chassis components. According to given

estimations, use of 6000 series alloys will be reasonable in a smaller number of positions in cars. The

production of alloys of 6000 series will mostly be a privilege of big companies having a necessary

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equipment, and they will further have an important place for a sophisticated structures such as planes,

space aircrafts etc.

5. CONCLUSION

A car mass is a very important factor influencing the fuel consumption. This aspect affects the resistances

and forces that are to be overcome, and which are directly confronted to the movement of a car. A smaller

car mass lead to a smaller fuel consumption. According to this, car manufacturers tend to reduce a mass

of car chassis. They do it in a manner that they use aluminium and its alloys instead of iron and its alloys.

They use plastics and composite materials with which they make some parts of a chassis and interior of a

car. Not only a chassis is lighter but also it is stronger and better absorbs impacts. On the other side, the

reduction of a certain chassis mass and car engine opens a possibility of embedding of additional safety

systems, reinforcement of a chassis etc.

With regard to the limit of reserves of crude oil, strict demands prescribed by leading countries in the

world in relation to the emission of dangerous gasses, trend to offer a buyer more economical car, all

measures influence the reduction of an entire car mass and smaller fuel consumption, still will be a main

goal of leading car manufacturers and leader in the development of car industry.

6. REFERENCES

[1] S.K. Das, H.W. Hayden, G.B. Barthold, Development of Non-Heat-Treatable Automotive

Aluminium

Sheet Alloys, Materials Science Forum-Trans Tech Publications, Switzerland, 331-337(2000)

[2] J.M. Story, G.W.Jarvis, H.R. Zonke, S.J. Murtha, Issues and Trends in AutomotiveAluminium Sheet Forming, Alcoa, SAE Paper No930277(1993).

[3] Boidar Nikoli, Danilo Nikoli, Radoje Vujadinovi,Motorna vozila I, DANU, Podgorica 2006.

[4] Batakovi Mirjana Uticaj mase vozila na potronju goriva - Diplomski rad: Mainski fakultet,

Podgorica, 2012. godine.

[5] Primena aluminijuma u automobilskoj industriji (http://mfkg.kg.ac.rs/centri-fakulteta/centar-

za-virtuelnuproizvodnju/download/SZnanja/AlMgVC/1.%20Primena%20aluminijuma%20u

%20automobilskoj%20industriji.pdf);

[6] http://www.drivealuminum.org

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