Most Viewed The properties of aluminum and its alloys

The properties of aluminum

Physical properties of aluminum

main Physical properties of aluminum and aluminum alloy, which are useful for the application:

density or specific gravity;
the melting temperature;
thermal expansion coefficient;
thermal conductivity;
conductivity.

These aluminum properties are presented below in tables [1]. They can only be considered as a basis for comparison alloys and their states and should not be used for engineering calculations. They are not guaranteed values, since in most cases they are the average values for products with different sizes, forms and methods of manufacture. Therefore, they may not be exactly representative of the products of all sizes and shapes.

Density ratings for popular aluminum alloys are based on annealed condition (O). Differences in density due to the fact, that alloys have different alloying elements and in different amounts: silicon and magnesium are lighter than aluminum (2.33 and 1,74 g / cm³), and iron, manganese, copper and zinc are heavier (7.87; 7,40; 8,96 and 7,13 g / cm³).

Effect of alumina and the physical properties of, in particular, its density, on structural characteristics of aluminum alloys cm. here.

Aluminum as a chemical element

Aluminum It is the third most common - after oxygen and silicon - among about 90 chemical elements, which is found in the Earth's crust.
Among metal elements - he first.
This metal has many useful properties, physical, mechanical, technological – thanks to which it is widely used in all spheres of human activity.
Aluminum - a malleable metal, which is silvery white in color and is easily processed by most metal forming methods: rolling, drawing, extrusion (pressing), forging.
Its density - specific weight - is about 2,70 grams per cubic centimeter.
Pure aluminum is melted at a temperature 660 degrees Celcius.
Aluminum has a relatively high thermal conductivity and electrical conductivity.
In the presence of oxygen is always covered with a thin, invisible oxide film. This film is substantially impermeable and has a relatively high protective properties. Therefore, the aluminum usually shows stability and long life under normal atmospheric conditions.

The combination of properties of aluminum and its alloys

Aluminum and its alloys have a unique combination of physical and other properties. This is made of aluminum with one of the most versatile, cost-effective and attractive construction and consumer materials. Aluminum is used in a very wide range - from soft, very plastic packaging foil to the most demanding space projects. Aluminum is considered as the second after steel among numerous constructional materials.

low density

Aluminum - is one of the most light industrial construction. Aluminum density is about three times lower, than steel or copper. This physical property ensures a high specific strength - strength per unit weight.

Figure 1.1 – The volume per unit weight of aluminum in comparison with other metals [3]

Figure 1.2 – The influence of alloying elements on
strength properties, hardness,
fragility and plasticity [3]

Figure 1 – Strength per unit of density of aluminum in comparison with various metals and alloys [3]

Figure 2 – Tensile curves of aluminum in comparison 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.

ferry catamarans,
oil tankers and
planes -

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

Figure 3 - Density of aluminum depending on its purity and temperature [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 4
a - natural oxide coating on ultrapure aluminum;
b - purity aluminum corrosion 99,5 % with a natural oxide coating
in a corrosively aggressive environment [2]

Figure 5.1 – The effect of alloying elements on corrosion resistance and fatigue strength [3]

Figure 5.2 – Pitting corrosion (pitting corrosion) of aluminum sheets
alloy 3103 in various corrosive conditions [3]

Strength

The strength properties of pure aluminum are rather low (figure 6). However, these mechanical properties can grow very, If aluminum is added in the alloying elements and, Moreover, it is subjected to thermal (figure 6) or deformation (figure 7) strengthening.

Typical alloying elements are:

manganese,
silicon,
copper,
magnesium,
and zinc.

Figure 6 - Influence of purity of aluminum on its strength and hardness [2]

Figure 7 - 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 – The mechanical properties of aluminum 99,50 %
depending on the degree of cold deformation obtained [2]

Figure 2 – Influence of alloying elements on density and Young's modulus [3]

Durability at low temperatures

It is known, that the steel becomes brittle at low temperatures. aluminum also, in front of, at low temperatures, it increases its strength and maintains a high viscosity. It is this physical property has enabled its use in space vehicles, working conditions in the cold space.

Figure 9 – Changing the mechanical properties of aluminum alloy 6061
with decreasing temperature

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 10 – Thermal conductivity of aluminum in comparison 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 11 - Reflective properties of aluminum [2]

Figure 12 – Reflective properties and emissivity of aluminum with various surface treatments [3]

Figure 13 – Comparison of the reflective properties of different 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 14 – Electrical properties of aluminum [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 15 – Magnetizability of aluminum alloy AlCu [3]

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 16 – 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 physical property is used at higher structural fire safety measures, for example, offshore oil rigs.

At the same time, with increasing temperature above 100 degrees Celsius, the strength of aluminum alloys is significantly reduced (figure 17).

Figure 17 – The tensile strength of aluminum alloy 2014-T6
at various 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.
There are hardly any restrictions form profiles, which are obtained from this metal by extrusion (pressing).