The International Annealed Copper Standard (IACS) is a

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object ...

established in 1914 by the United States Department of Commerce. It is an empirically derived standard value for the

electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...

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 National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...

. The average resistance of the samples was determined to be 0.15292 Ω for copper wires with a mass of 1

gram The gram (originally gramme; SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram. Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to th ...

of uniform

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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 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. 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 An aluminium alloy (or aluminum alloy; see spelling differences) is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin, nickel and zinc. There are two pr ...

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. The acceptance criteria for electrical conductivity of finished or semi-finished parts of wrought aluminum alloys are contained in

SAE International SAE International, formerly named the Society of Automotive Engineers, is a United States-based, globally active professional association and standards developing organization for engineering professionals in various industries. SAE Internati ...

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 ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...

specification ASTM E 1004 Electromagnetic (Eddy-Current) Measurements of Electrical Conductivity. Electrical conductivity meters with direct readout in %IACS are commercially available.

References

{{reflist Copper International standards