Thus, for example all alloys up to 80% Ni are paramagnetic at 150 ✬ while at 20 ✬ alloys containing more than 68.5% nickel exhibit ferromagnetic behaviour.įigure 5. A two-phase area in which liquid and a crystals co-exist is formed between liquidus and solidus.īelow a dotted straight line at the bottom right, behaviour is ferromagnetic, above it is paramagnetic.
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The curve which forms the upper boundary of the area of a crystals is termed the ‘solidus’. The upper curve, which forms the lower boundary of the liquid melt, is called the ‘liquidus’. The melting points of the two components broaden to a melting range in the alloys. The equilibrium diagram is therefore very simple. the Cu-Ni system exhibits complete solubility in both liquid and solid states.
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Īlloys of the two metals form a continuous series of solid solutions having a face-centred cubic lattice, i.e. The equilibrium diagram was first established by Gürtler and Tammann and was later improved by Pilling and Kihlgren, among others. Around 1925, it was recognised that additions of iron significantly improve the resistance of Cu-Ni alloys to erosion corrosion in flowing seawater and other aggressive waters. The Cu-Ni alloys with additions of manganese that are important in electrical engineering were first referred to in 1895 in a paper of the Physikalisch-Technischen Reichsanstalt in Berlin on ‘Electrical properties of Cu-Ni alloys’. In Germany, the description ‘Cu-Ni alloys’ was in general use for the group of materials containing less than 50% Ni (see 1.). In England, the term ‘cupronickel’ was used at the start of the 20th century for an alloy of 80% Cu and 20% Ni. It was only red nickel pyrites (NiAs), for the veins of ore worked in seams also incorporated copper and iron sulphides as well as arsenides. However, they would not succeed in extracting copper from it – a spell was cast on the ore by a ‘nickel’. In the Middle Ages, Saxon miners gave a mineral, from whose red colour they inferred a copper ore, the nickname ‘coppernickel’ (nickel = goblin = mountain troll). These and many other old coins are outstanding examples for the high corrosion resistance of Cu-Ni alloys.
to the former German 50-Pfennig and 1 DM pieces (approximately 75% Cu and 25% Ni). It was found in Bactria and consists of an alloy similar e.g. The most ancient Cu-Ni coin that has been saved for posterity comes from the period around BC 235. This is confirmed by finds of coins from antiquity, which contain up to 10% nickel in addition to copper.
(DKI A 4049) Cu-Ni equilibrium diagram 1.1 HistoricalĪlthough elemental nickel was only discovered relatively late on, its use in alloys – without knowledge of the alloy composition – goes back at least two thousand years. In European standards, these alloys are assigned to ‘low-alloyed copper alloys’ (see CR 13388 and relevant product standards).įigure 1. The age-hardenable copper-nickel-silicon alloys with 1.0 to 4.5% Ni and 0.2 to 0.6% Be are not dealt with here. When other elements are present, nickel has the largest individual content after copper, compared with each other element.Īs with other copper alloys, it is necessary to distinguish between wrought alloys, which are processed to semi-finished products, and cast alloys, from which castings are produced by various casting processes.Īpart from 8.5 to 45% Ni, most commercial alloys usually contain manganese, iron and tin to improve specific properties, cast alloys also have additions of niobium and silicon. 10 -8cm).Ĭu-Ni alloys are alloys of copper (base metal with the largest individual content) and nickel with or without other elements, whereby the zinc content may not be more than 1%. The lattice spacing of the face-centre cubic solid solution varies almost linearly with atomic concentration between the values for copper (3.6153. Cu-Ni alloys crystallise over the whole concentration range in a face-centred cubic lattice. Ĭopper and nickel are adjacent to one another in the periodic system of elements, with atomic numbers 29 and 28 and atomic weights 63.54 and 68.71.The two elements are closely related and are completely miscible in both the liquid and solid state.
Today, Cu-Ni alloys have gained a variety of interesting applications because of their specific characteristics. However, Cu-Ni alloys were in existence much earlier, mostly prepared by processing ores.
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