Copper alloys are alloys based on copper, in which the main alloying elements are Zn, Sn, Si, Al, Ni. Cu-based alloys constitute mostly substitutional solid solutions, for which solute or impurity atoms replace or substitute for the host atoms. Several features of the solute and solvent atoms determine the degree to which the former dissolves in the latter. These are expressed as the Hume–Rothery rules. There are as many as 400 different copper and copper alloy compositions loosely grouped into the categories: copper, high copper alloy, brasses, bronzes, copper nickels, copper–nickel–zinc (nickel silver), leaded copper, and special alloys. In addition, a limited number of copper alloys can be strengthened by heat treatment.; consequently, cold working and/or solid-solution alloying must be used to improve these mechanical properties.
Types of Copper Alloys
As was written, there are as many as 400 different copper and copper alloy compositions loosely grouped into the categories: copper, high copper alloy, brasses, bronzes, copper nickels, copper–nickel–zinc (nickel silver), leaded copper, and special alloys. In following points we summarize key properties of selected copper-based materials.
Electrolytic-tough pitch (ETP) copper. Electrolytic tough pitch copper, UNS C11000, is pure copper (with a maximum of 0.0355% of impurities) refined by electrolytic refining process and it is the most widely used grade of copper all over the world. ETP has a minimum conductivity rating of 100% IACS and is required to be 99.9% pure. It has 0.02% to 0.04% oxygen content (typical). Electrical wiring is the most important market for the copper industry. This includes structural power wiring, power distribution cable, appliance wire, communications cable, automotive wire and cable, and magnet wire. Roughly half of all copper mined is used for electrical wire and cable conductors. Pure copper has the best electrical and thermal conductivity of any commercial metal. The conductivity of copper is 97% that of silver. Due to its much lower cost and greater abundance, copper has traditionally been the standard material used for electricity transmission applications.- Brass. Brass is is the generic term for a range of copper-zinc alloys. Brass can be alloyed with zinc in different proportions, which results in a material of varying mechanical, corrosion and thermal properties. Increased amounts of zinc provide the material with improved strength and ductility. Brasses with a copper content greater than 63% are the most ductile of any copper alloy and are shaped by complex cold forming operations. Brass has higher malleability than bronze or zinc. The relatively low melting point of brass and its fluidity make it a relatively easy material to cast. Brass can range in surface color from red to yellow depending on the zinc content. Some of the common uses for brass alloys include costume jewelry, locks, hinges, gears, bearings, hose couplings, ammunition casings, automotive radiators, musical instruments, electronic packaging, and coins. Brass and bronze are common engineering materials in modern architecture and primarily used for roofing and facade cladding due to their visual appearance.
- Bronze. The bronzes are a family of copper-based alloys traditionally alloyed with tin, but can refer to alloys of copper and other elements (e.g. aluminum, silicon, and nickel). Bronzes are somewhat stronger than the brasses, yet they still have a high degree of corrosion resistance. Generally they are used when, in addition to corrosion resistance, good tensile properties are required. For example, beryllium copper attains the greatest strength (to 1,400 MPa) of any copper-based alloy.
- Copper-nickel Alloy. Cupronickels are copper-nickel alloys that contain typically from 60 to 90 percent of copper and nickel as the main alloying element. The two main alloys are 90/10 and 70/30. Other strengthening elements, such as manganese and iron, may be also contained. Cupronickels have excellent resistance to corrosion caused by sea water. Despite its high copper content, cupronickel is silver in colour. The addition of nickel to copper also improves strength and corrosion resistance, but good ductility is retained.
- Nickel Silver. Nickel silver, known also as German silver, nickel brass or alpacca, is a copper alloy with nickel and often zinc. For example, UNS C75700 nickel silver 65-12 copper alloy has good corrosion and tarnish-resistance, and high formability. Nickel silver is named due to its silvery appearance, but it contains no elemental silver unless plated.
Hardness of Copper Alloys
Vickers hardness of electrolytic-tough pitch (ETP) copper depends greatly on the temper of the material, but it is between 50 – 150 HV.
Brinell hardness of carthridge brass – UNS C26000 is approximately 100 MPa.
Brinell hardness of aluminium bronze – UNS C95400 is approximately 170 MPa. The hardness of aluminum bronzes increases with aluminum (and other alloy) content as well as with stresses caused through cold working.
Brinell hardness of tin bronze – UNS C90500 – gun metal is approximately 75 BHN.
Rockwell hardness of copper beryllium – UNS C17200 is approximately 82 HRB.
Brinell hardness of cupronickel – UNS C70600 is approximately HB 100.
Rockwell hardness of nickel silver – UNS C75700 is approximately 45 HRB.
Rockwell hardness test is one of the most common indentation hardness tests, that has been developed for hardness testing. In contrast to Brinell test, the Rockwell tester measures the depth of penetration of an indenter under a large load (major load) compared to the penetration made by a preload (minor load). The minor load establishes the zero position. The major load is applied, then removed while still maintaining the minor load. The difference between depth of penetration before and after application of the major load is used to calculate the Rockwell hardness number. That is, the penetration depth and hardness are inversely proportional. The chief advantage of Rockwell hardness is its ability to display hardness values directly. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale.
The Rockwell C test is performed with a Brale penetrator (120°diamond cone) and a major load of 150kg.
We hope, this article, Hardness of Copper Alloys, helps you. If so, give us a like in the sidebar. Main purpose of this website is to help the public to learn some interesting and important information about materials and their properties.
