Aluminium 

Functional properties of aluminum

Aluminum and its alloys have important functional properties, which provide their wide application in many areas of human activity.

Сorrosion resistance

There is always a thin natural oxide film on the aluminum surface.. This film is firmly "attached" to the base metal. Therefore, it provides most aluminum alloys with a significant corrosion resistance in many atmospheric and chemical environments. Especially distinguished in this series alloys 1xxx, 3xxx, 5xxx and 6xxx.

Fig. 1 – The surface oxide film is natural source of corrosion protection [TALAT 1252] [1]

Thermal conductivity

  • Aluminum and aluminum alloys are good conductors of heat. The thermal conductivity of aluminum alloy is more than four times higher, than that of carbon steels.
  • They begin to melt at a much lower temperature, than steel.
  • The melting point of pure aluminum is about 660 ° C.
  • Aluminum alloys, depending on the degree of alloying, begin to melt at lower temperatures, for example, at 515 ° C for alloy 2017.

Fig. 2 – Thermal Conductivity of Aluminium Compared with other Metals [TALAT 1501] [1]


Fig. 3 – Solidification of pure aluminium [TALAT 1201] [1]

Сonductivity

Pure aluminum and some of its alloys have very high electrical conductivity (low electrical resistance). Among the metals, which are used as electricity conductors, in this they are second only to copper. At the same time, on high-voltage power lines, it is usually used precisely aluminum wires. They have a larger cross-section, than the equivalent copper wire, however and half the weight. This allows, in particular, less put the support and reduce their height.

Fig. 4 – Electrical Properties of Aluminium [TALAT 1501] [1]

Strength to weight ratio

High strength/weight ratio (relatively high strength at low density) determines the high efficiency of aluminum alloys as structural materials. Therefore, this opens up wide opportunities for replacing heavier metals with aluminum without losing the bearing capacity of the product or part.. This feature of aluminum alloys, combined with good corrosion resistance, provides them with a wide range of applications., for example, in transport engineering (aircraft, cars, passenger cars).


Fig. 5 – Volume per Unit Weight [TALAT 1501] [1]

Aluminum at low temperatures

Aluminum alloys, especially alloys series 3xxx, 5xxx and 6xxx ideally suited for operation at low temperatures. Numerous data confirm, their ductility and toughness, as well as strength, above at low temperatures, down to absolute zero, than at "room" temperature.

Fig. 6 – Tensile Properties of 6061 Alloy Heat Treated, Artifically Aged [TALAT 1501] [1]

Тechnological processing

Aluminum alloys are easily processed by most known metal forming technologies and are particularly easy to extrude.. Extrusion is the process of forcing heated metal through a die., forming profiles with complex cross-sections. This property of aluminum alloys makes it possible to produce from them extruded profiles with a virtually unlimited variety of cross-sectional shapes. This allows you to have the metal in those areas and thus, to ensure that the profile of the maximum load-bearing capacity under the influence of the given loads.

Fig. 7 – Single Stand Hot Mill [TALAT 1301] [1]

Fig. 8 – Forward or Direct Extrusion [TALAT 1302] [1]

Methods aluminum compound

Details of aluminum alloy are joined by a large number of ways, including, quarrel, rations, riveting, screw connections. welding of aluminum may seem difficult for those, who has experience only with steels and try to move it to the aluminum. Welding aluminum alloys consider pretty easy, when used proven techniques such, like consumable arc welding (ME) and tungsten non-consumable electrode (TIG) in an inert gas environment.


Fig. 9 – Joining Systems for Thin-Walled Aluminium Components [TALAT 4101] [1]

Reflectivity and emissivity

Emissivity – it's lightness, with which the substance radiates its own thermal energy. It is closely related to reflectivity: the best reflective surface is the worst emitter., and, conversely, the worst reflective surface is the best emitter.

Ordinary aluminum reflects about 75% light falling on it and 90% thermal radiation. However, the emissivity of the same aluminum is low. He makes up <10% from the emissivity of a black body at the same temperature and in the same environment. The combined properties of high reflectivity and low emissivity lead to the use of aluminum foil as a reflective insulating medium [1].

Fig. 10 – Reflectivity and Emissivity of Aluminium with Various Surface Treatments [1501] [1]


Fig. 11 – Comparison of Reflectivity of Various Metals [1501] [1]

aluminum recycling

An important characteristic of the alloys is aluminum, what their isworn cycle almost completely enclosed They are easy to reuse – retsiklingu. Unlike other construction materials, they are processed almost the same high-quality products.


Fig. 12 – Aluminium Production from Scrap Recycling [TALAT 1100] [1]

Fig. 13 – Energy Needs for Primary and Recycled Aluminium.
Energy savings of up to 95% are achieved per tonne of aluminium produced from scrap compared to primary aluminium [2].

Sources:

  1. TALAT Lectures
  2. Aluminium Recycling in Europe The Road to High Quality Products – EAA/OEA Recycling Division