Useful properties of aluminium

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Particularly useful properties of aluminum for its use in technology, production and everyday life are:

low density;
high corrosion resistance;
high thermal conductivity;
high electrical conductivity.

Aluminum as a chemical element

Third most abundant - after oxygen and silicon - among about 90 chemical elements, which is found in the Earth's crust.
Among metal elements - he first.
Has many beneficial properties, physical, mechanical, technological – thanks to which it is widely used in all spheres of human activity.
Malleable metal, which is silvery white in color and is easily processed by most metal forming methods: rolling, drawing, extrusion (pressing), forging.
Density is approx. 2,70 grams per cubic centimeter.
The point of melting pure aluminum is about 660 degrees Celcius.
Has relatively high coefficients of thermal conductivity and electrical conductivity.
In the presence of oxygen is always covered with a thin, invisible oxide film. This film is largely impenetrable and does a fairly good job of protecting the metal inside from corrosion..

Combination of aluminum properties

Low density

Aluminum - is one of the most light industrial construction.
Density of aluminium approximately three times lower, than steel or copper.
This gives high specific strength - strength per unit mass.

Figure 1 – Volume per Unit Weight [3]

Figure 2 – The Effect of Alloying Elements on Tensile Strength, hardness, Impact Sensibility and Ductility [3]

Figure 3 – Density-Related Strength of Aluminium in Comprasion with Various Metals and Alloys [3]

Figure 4 – Stress-Strain Curves of Aluminium in Comparision with Various Metals and Alloys [3]

Therefore, the aluminum alloys are widely used in transport engineering to increase the capacity of vehicles and fuel economy.

Passenger carriages
ferry catamarans,
Oil tankers and
Airplanes –

Here are the best examples of the use of aluminum in transport.

Figure 5 – The Effects of Aluminium Purity and Temperature on Aluminium Density [2]

Сorrosion resistance

Aluminum has a high corrosion resistance due to a thin layer of aluminum oxide on its surface,. This oxide film is formed instantly, as soon as the fresh aluminum surface comes into contact with air (figure 4). In many cases, this property allows the use of aluminum without any special surface treatment. If you need additional protective or decorative coating, the applied anodizing or painting the surface.

Figure 6
a – natural oxide film on ultra-pure aluminum;
b – corrosion of aluminum with a purity of 99.5% with a natural oxide film
in a corrosion-aggressive environment [2]

Figure 7 – The Effects of Alloying Elements on Corrosion Resistance and Fatigue Strength [3]

Figure 8 – Pitting Corrosion Behaviour of 3103 Mill Finish Aluminium Sheet [3]

Strength

The strength properties of pure aluminum are rather low (figure 9). Mechanical properties can increase:

when adding alloying elements
thermal hardening (Figure 10)
strain hardening (Figure 11).

Typical alloying elements are:

manganese,
silicon,
copper,
magnesium,
zinc.

Figure 9 - Influence of purity of aluminum on its strength and hardness [2]

Figure 10 - Mechanical properties of high-purity wrought
aluminum-copper alloys in various states [2]
(O - annealed, W - immediately after the tempering, T4 - naturally aged, T6 - artificially aged)

Figure 8 – Mechanical properties of aluminum 99,50 %
depending on the degree of cold deformation obtained [2]

Figure 11 – The Effect of Alloying Elements on Density and Young’s Modulus [3]

Durability at low temperatures

Steel becomes brittle at low temperatures.
Aluminum at low temperatures increases its strength and maintains high toughness.
This property makes it possible to use aluminum in space cold conditions.

Figure 12 – Tensile Properties of 6061 Alloy Heat Treated, Artifically Aged [3]

Thermal conductivity

Aluminum conducts heat three times faster, than steel. This physical property is very important in heat exchangers to heat or cool the working environment. here – extensive use of aluminum and its alloys in cookware, air conditioners, primyshlennom and automotive heat exchangers.

Figure 13 – Thermal Conductivity of Aluminium
Compared with other Metals [3]

Reflectivity

Aluminum is an excellent reflector of radiant energy over the entire range of wavelengths. This physical property makes it possible to use it in devices, which work against ultraviolet spectrum through the visible spectrum to the infrared spectrum and thermal waves, as well as such electromagnetic waves, like radio waves and radar waves [1].

Aluminum has the ability to reflect more 80 % light waves, which provides it with widespread use in lighting devices (figure 11). Due to the physical properties, it is used in thermal insulation materials. for instance, aluminum roofing reflects a large proportion of the solar radiation, that provides indoor air cool in the summer and, in the same time, It retains heat the room in winter.

Figure 14– Reflectivity of Aluminium [2]

Figure 15 – Reflectivity and Emissivity of Aluminium
with Various Surface Treatments [3]

Figure 16 – Comparison of Reflectivity of Various Metals [3]

Electrical properties

Aluminum is one of the two available metal, which have sufficiently high electrical conductivity, to apply them as electrical conductors.
Electrical conductivity "electric" brand aluminum 1350 is about 62 % from the international standard IACS - the electrical conductivity of annealed copper.
However, the specific weight of aluminum is only one third of the specific weight of copper. It means, that he spends twice as much electricity, than copper of the same weight. This physical property allows aluminum to be widely used in high voltage power lines (PTL)., transformer, electric buses and socket light bulbs.

Figure 17 – Electrical Properties of Aluminium [3]

Magnetic properties

Aluminum has the property not to be magnetized in electromagnetic fields. This makes it useful in protecting the equipment from exposure to electromagnetic fields. Another application of this feature is computer discs and parabolic antenna.

Figure 18 – Magnetic Susceptibility of AlCu Alloy [3]

No toxic properties

This property of aluminum - no toxicity - was discovered at the beginning of its industrial development. It is this property of aluminum has enabled its use for the manufacture of kitchen utensils and appliances, without any harmful effects to the human body. Aluminum with its smooth surface is easy to clean, it is important to ensure high hygiene when cooking. Aluminium foil and containers widely and safely used in the packaging of a direct contact with food.

Sound insulation properties

This property makes aluminum a use when performing acoustic ceilings.

The ability to absorb impact energy

Aluminum has a modulus three times smaller, than steel. This physical property makes it a great advantage for the manufacture of automobile bumpers and other car security funds.

Figure 19 – Automotive aluminum profiles
to absorb impact energy in an accident

Fireproof properties

Aluminum pieces forms no sparks upon impact against each other, as well as other non-ferrous metal. This is important for use with increased fire safety measures for structures.
At the same time, with increasing temperature above 100 degrees Celsius, the strength of aluminum alloys is significantly reduced (Figure).

Figure 20 – Tensile Strength of 2014-T6 at Test Temperatures [3]

Technological properties

Ease, with which the aluminum can be processed into any form – workability, It is one of the most important of its advantages. Very often it can successfully compete with the cheaper materials, which are much more difficult to handle:

This metal may be molded by any method, which is known to metallurgists, foundry.
It can be rolled up to thicknesses of up to foil, thinner sheets of paper which.
Aluminum plates can be stamped, It extends, planted and mold all known methods of metal forming.
Aluminum can be forged by all means of forging
aluminum wire, dragged from a round bar, It may then be woven into electric cables of any type and size.
Almost no shape restrictions extruded profiles, in which it is prepared from this metal extrusion.