International Annealed Copper Standard

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The International Annealed Copper Standard (IACS) is a standard established in 1914 by the United States Department of Commerce. [1] It is an empirically derived standard value for the electrical conductivity of commercially available copper.

Sometime around 1913 several copper samples from 14 important refiners and wire manufacturers were analyzed by the U.S. Bureau of Standards. The average resistance of the samples was determined to be 0.15292 Ω for copper wires with a mass of 1 gram of uniform cross section and 1 meter in length at 20 °C. In the United States this is usually written as "0.15292 ohm (meter, gram) at 20 °C".

Germany proposed a slight modification of this value to "0.15328 ohm (meter, gram) at 20 °C", this being equivalent to a conductivity of exactly 58×106  S/m at 20 °C. The German modification was adopted by the International Electrotechnical Commission in 1913 and subsequently published by the United States Department of Commerce on October 1, 1914 as the International Annealed Copper Standard (IACS).

The standard is most often used as a comparative property in the specification of the conductivity of other metals. For example, the conductivity of a particular grade of titanium may be specified as 1.2 % IACS, meaning that its electrical conductivity is 1.2 % of the copper specified as the IACS standard. [2]

The standard can be found at https://archive.org/stream/copperwiretables31unituoft#page/n0/mode/1up.

Quality of aluminum alloys

Heat treatment will alter several properties of an alloy, many of which are important to a design engineer. A measurement of the electric conductivity of aluminum alloys can be used to verify that a heat treatment process has been done correctly. For example a component made of "7075" alloy which was correctly treated with the process "T73" to gain resistance to stress corrosion cracking will fall in the range of 38.0 to 43.0 % IACS. [3]

The acceptance criteria for electrical conductivity of finished or semi-finished parts of wrought aluminum alloys are contained in SAE International specification AMS2658 Hardness and Conductivity Inspection of Wrought Aluminum Alloy Parts. Here the values are given in reference to the IACS.

A method for measuring electrical conductivity is described in ASTM International specification ASTM E 1004 Electromagnetic (Eddy-Current) Measurements of Electrical Conductivity. Electrical conductivity meters with direct readout in %IACS are commercially available. [4]

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1100 aluminium alloy is an aluminium-based alloy in the "commercially pure" wrought family. With a minimum of 99.0% aluminium, it is the most heavily alloyed of the 1000 series. It is also the mechanically strongest alloy in the series, and is the only 1000-series alloy commonly used in rivets. At the same time, it keeps the benefits of being relatively lightly alloyed, such as high electrical conductivity, thermal conductivity, corrosion resistance, and workability. It can be hardened by cold working, but not by heat treatment.

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3004 aluminium alloy is an alloy in the wrought aluminium-manganese alloys family. It is similar to the 3003 alloy, except for the addition of approximately 1% magnesium. It can be cold worked to produce tempers with a higher strength but a lower ductility. Like most other aluminium-manganese alloys, 3003 is a general-purpose alloy with moderate strength, good workability, and good corrosion resistance. It is commonly rolled and extruded, but typically not forged. As a wrought alloy, it is not used in casting.

3102 aluminium alloy is an alloy in the wrought aluminium-manganese family. It is one of the most lightly alloyed grades in the 3000 series, with at least 97.85% aluminium by weight. Like most other aluminium-manganese alloys, 3102 is a general-purpose alloy with moderate strength, good workability, and good corrosion resistance. Being lightly alloyed, it tends on the lower strength and higher corrosion resistance side. It can be cold worked to produce tempers with a higher strength but a lower ductility. It can be formed by rolling, extrusion, and forging. As a wrought alloy, it is not used in casting.

5154 aluminium alloy is an alloy in the wrought aluminium-magnesium family. As an aluminium-magnesium alloy, it combines moderate-to-high strength with excellent weldability. 5154 aluminium is commonly used in welded structures such as pressure vessels and ships. As a wrought alloy, it can be formed by rolling, extrusion, and forging, but not casting. It can be cold worked to produce tempers with a higher strength but a lower ductility. It is generally not clad.

5454 aluminium–magnesium alloy is an alloy in the wrought aluminium-magnesium family. It is closely related to 5154 aluminium alloy. As an aluminium-magnesium alloy, it combines moderate-to-high strength with excellent weldability. Like 5154, 5454 aluminium is commonly used in welded structures such as pressure vessels and ships. As a wrought alloy, it can be formed by rolling, extrusion, and forging, but not casting. It can be cold worked to produce tempers with a higher strength but a lower ductility. It is generally not clad.

5456 aluminium–magnesium alloy is an alloy in the wrought aluminium-magnesium family. While it is closely related to 5356 aluminium alloy, it is used in structural applications, like most other aluminium-magnesium alloys, and not as filler for welding. As a wrought alloy, it can be formed by rolling, extrusion, and forging, but not casting. It can be cold worked to produce tempers with a higher strength but a lower ductility. It is susceptible to exfoliation corrosion when held at temperatures above 65 °C (150 °F) for extended periods of time.

6005A aluminium alloy is an alloy in the wrought aluminium-magnesium-silicon family. It is closely related, but not identical, to 6005 aluminium alloy. Between those two alloys, 6005A is more heavily alloyed, but the difference does not make a marked impact on material properties. It can be formed by extrusion, forging or rolling, but as a wrought alloy it is not used in casting. It cannot be work hardened, but is commonly heat treated to produce tempers with a higher strength at the expense of ductility.

6262 aluminium alloy is an alloy in the wrought aluminium-magnesium-silicon family. It is related to 6162 aluminium alloy, but sees much more widespread use. It is notably distinct from 6162, and most other aluminium alloys, in that it contains lead in its alloy composition. It is typically formed by extrusion, forging, or rolling, but as a wrought alloy it is not used in casting. It can also be clad, but that is not common practice with this alloy. It cannot be work hardened, but is commonly heat treated to produce tempers with a higher strength but lower ductility.

References

  1. Copper Wire Tables, (Technical report). Circular of the Bureau of Standards No.31 (3d ed.). United States Department of Commerce. October 1, 1914.
  2. "Resistivity and Conductivity Units Converter".
  3. "Stress Corrosion Cracking of Aluminum Alloys". Total Materia. June 2001. Retrieved 14 April 2016.
  4. "Eddy Current Conductivity Meter for Metals". Zappitec. Retrieved 26 September 2018.