Kupfer-Nickel-Legierungen CuNi

Copper-nickel alloys are alloys of copper (the base metal is copper with the largest single content) and nickel, with or without other elements. These alloys, by definition, may not have a zinc content of greater than 1%.  When other elements are present in the alloy, nickel, after copper, has a higher percentage content than the other elements. 

As with other copper materials, a distinguishment is made between alloys that are processed into semi-finished products and alloys used for casting.

In addition to the typical Ni content between 8.5 to 45%, conventional alloys typically also contain manganese, iron and tin.  Casting alloys normally include additions of niobium and Silicon.

Properties of Copper-nickel alloys

Copper-nickel alloys have interesting physical properties, good strength values (even under continuous stress and elevated temperatures), and a high corrosion resistance to many elements, particularily seawater.

Nevertheless, the properties of the binary copper-nickel alloys are often still not sufficient for some applications.  The properties of these alloys can however be greatly improved with additional Elements, particularily manganese, iron and tin and niobium and silicon, as well as chromium, beryllium and aluminum.

Physical Properties

The nickel content of copper-nickel alloys has a big impact on the color. The copper color is brighter with increasing nickel additive.  Starting at apporximately 15% Ni, the alloy appears nearly silver-white. Gloss and purity of color increases with the nickel content.  From about 40% Ni, the polished surface of the alloys is hardly distinguishable from that of silver.

The density of copper (8.93 kg / dm3 at 20 ° C) is not greatly influenced with increasing nickel content (density of nickel at 20 ° C = 8.90 kg /dm3). The desnsity for all copper-nickel alloys is a constant  8.9 kg/dm3.  The high thermal conductivity of pure copper of 394 W / (m * K) is however greatly reduced with the addition of nickel (Figure 7). At 45% Ni, the thermal conductivity reaches the low value of 21 W / (m * K).  With increasing nickel content, the longitudinal expansion coefficient increases sharply at first and then more slowly (Figure 8). At 20 ° C, the specific heat of copper is 0.385 J / (g · K) and of nickel at 0.452 J / (g · K). With increasing nickel content the specific heat decreases slightly at first and then levels out to an average value of 0.377 J / (g · K).

All physical properties of the two copper-nickel alloys, CuNi10Fe1Mn and CuNi30Mn1Fe have been thoroughly examined and are well known for conditions at room temperature up to 1000 ° C [8].



Electrical Properties


The electrical resistivity of the copper-nickel-resistance alloys is specified for different temperatures in Figure 8.  The resistivity increases greatly with increased nickel content.  Thus, copper-nickel alloys are suitable as resistance materials and hits a maximum resistivity value at a nickel content of 45%. The minimum value of the temperature coefficient of electrical resistivity also occures with a nickel content of 45% (Figure 9).

Particularly noteworthy is the high thermoelectric power of copper-nickel alloys (with nickel content between 40 and 50% Ni) compared to that of other metals such as iron (Figure 10), copper, platinum, etc. They are therefore idealy suited for temperature measurement in a m edium temperature range for thermocouples.  In Figure 11, the thermoelectric power of CuNi44 is shown in relation to temperature and compared to that of copper and iron. The high thermal electric voltage of CuNi44 precludes its use as a resistivity material in low voltage electrical equipment, because the copper connections thermocouple with CuNi44.

Tab. 8 Kupfer-Nickel- Widerstandslegierungen nach DIN 17471

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Thermal Properties

The high thermal conductivity of pure copper of 394 W / (m * K) is greatly reduced with the inclusion of nickel (Figure 7).  Thermal conductivity reaches a low Point with a 45% Ni content at 21 W / (m * K).  The longitudinal expansion coefficient  increases with the addition of nickel concentrate more sharply at first and then at a slower rate (Figure 8).  The specific heat of copper is 0.385 J / (g · K) at 20 ° C and of nickel at 0.452 J / (g · K).  The specific heat decreases with increasing nickel content at first, but then levels out to an average value of 0.377 J / (g · K).

Magnetic Properties

Copper-nickel alloys do not exhibit ferromagnetism.  Copper is diamagnetic, nickel ferromagnetic. With an increase of nickel content, nickel-copper alloys move from the diamagnetic to the paramagnetic and finally into the ferromagnetic state.

Kupfer-Nickel-Legierungen zeigen keinen Ferromagnetismus. Kupfer ist diamagnetisch, Nickel ferromagnetisch. Nickel-Kupfer Legierungen gehen mit steigendem Nickelgehalt vom diamagnetischen über den paramagnetischen in den ferromagnetischen Zustand über.

Eisen hat je nach Legierung einen geringen Einfluss, wenn es in fester Lösung vorhanden ist. Liegt das Eisen in ausgeschiedener Form vor, so führen diese ferromagnetischen mikroskopischen Partikel zu einem makroskopischen Anstieg des Ferromagnetismus.

Die ausscheidungsfreie Matrix bleibt dia- bzw. paramagnetisch. Kupfer-Nickel-Legierungen mit 20 bis 25 % Ni und 20 % Fe oder etwa 25 % Co sind ausgesprochene Magnetwerkstoffe. Infolge ihrer hohen Remanenz und Koerzitivkraft eignen sie sich auch für Dauermagnete.

Mechanical Properties at Room Temperature


Copper-Nickel Wrought Alloys

Strength values for copper-nickel wrought alloy sheets and strips are listed in DIN EN 1652.  Additional data on the strengthes of semi-finished materials are also available. The alloy's strength will be denoted by an appending letter R, followed by a value (in MPa), such as CuNi30Mn1Fe R350.  For a strenght of R350, a minimum tensile strength of 350 N/mm2 is ensured.  The 0.2% yield strength and elongation at break are both determined by the strength conditions. The guaranteed minimum hardness (Vickers hardness) is shown by the letter H followed by the value, for example CuNi30Mn1Fe H110.

The tensile strength and elongation at break values for the copper-nickel resistance alloys are represented in Table 11. Figure 12 shows the increase in tensile strength, the 0.2% yield strength and hardness with the corresponding increase in nickel content. With an increase of strength there is only a small corresponding decline in elongation at break and necking. The notch impact strength is only slightly affected by the nickel content.

Iron has a favorable influence on the strength properties of copper-nickel alloys.  Figure 13 Shows an example of an alloy with 10% Ni content.  Improvements in the strength properties of CuNi30Mn1Fe be achieved by increasing both the iron and manganese contents by 2%. For example, strips and sheets made of alloy CuNi30Fe2Mn2 have a tensile strength of 440 n/mm2 and a 0.2% yield strength of 145 n/mm2.

Further increases in strength values can result with additives, such as aluminum or chrome.  These values are shown in Tab. 12.

As is the case with all metallic materials, the material's strength is increased with repeated cold working.  Copper-nickel alloys are no exception.  With increased cold working, the tensile strength improves by 0.2% yield strength and hardness, while, on the other hand, the elongation at break values decrease (Figure 14).

Copper-Nickel-Wrought Alloys

There are three curable copper-nickel wrought alloys particularily worth mentioning, those with additions of aluminum, chromium or beryllium.  The alloy with about 2% Al can be found in a cast or cured state.  With the addition of beryllium, the largest increase in strength is achieved after undergoing curing.  Such an alloy is already in use in the United States in marine technology [11].

High strenth, curable copper-nickel alloys with zinc content up to 6% , which usually contain other additives such as lead and zinc, are standardized in ASTMN 584.

Tab. 11 Kupfer-Nickel-Widerstandslegierungen nach DIN 17 471; Festigkeitseigenschaften bei 20 °C im weichgeglühten Zustand
Tab. 12 Mittlere Zusammensetzung und mechanische Eigenschaften praktisch bewährter Kupfer-Nickel-Knetlegierungen

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Mechanical Properties at Low and High Temperatures


Strength Properties at Low Temperatures

At low temperatures, copper-nickel alloys, like other copper materials, have excellent strength properties.  Image 15 shows the properties of an alloy containing 20% nickel.  As the temperature drops tensile strength increases without compromising the elongation at break and necking values.  Thus, these alloys exhibit no embrittlement at low temperatures and are thus well suited to cryogenic applications. 

Strength Properties at High Temperatures

Copper-nickel alloys also Display good strength characteristics at high temperatures.  Even with a relatively low nickel content, the alloy's high-temperature strength is improved.  Figure 16 shows the influence of the nickel content on the softening of cold rolled copper-nickel alloys at higher temperatures.  With the addition of iron, the strength characteristics are improved not only at room temperature but also at elevated temperatures.  Figure 17 Shows an example of a copper alloy with 10% Ni.  CuNi10Fe1Mn in temperatures up to 300°C and CuNi30Mn1Fe up to 350°C can, for example, be used in the production of pressure vessels.  When the temperature exceeds these limits, the strength values (in particular the creep strength and time yield Limit) decrease significantly (Figure 18).



The modulus of elasticity values decrease with increasing temperature at a rate of about 50-100 N / mm2 per ° C .

Not infrequently, metallic materials are exposed to elevated temperatures for a longer period of time. Thus, knowledge of the creep behavior of copper-nickel alloys is necessary.  These values are used to create a bench test. They are used to determine the material's behavior during static loading (stress state), taking into account the time under stress, and the tempertature, hence the term "creep behavior". Does not translate!

Er dient zur Ermittlung des Werkstoffverhaltens bei ruhender Beanspruchung (Standbeanspruchung) unter Bedingungen, bei denen neben den Einflüssen der Beanspruchungshöhe und der Temperatur ein wesentlicher Einfluss der Beanspruchungszeit vorhanden ist, daher der Begriff „Zeitstandverhalten“.

The creep rupture strength refers to the point at which a material can remain indefinitely without fracture, at a given temperatures and under a fixed weight.  The creep (time yield) limits referes to the point of time at which the material Begins to deform under certain temperature and stress conditions.

Table 15 provides values for the creep rupture strength and 1% of creep time yield limit for alloys CuNi10Fe1Mn and CuNi30Mn1Fe.  The values determine the temperature limits for the use of these alloys with long-term exposure.



Tab. 15 Zeitstandfestigkeit und 1%-Zeitdehngrenze für die Werkstoffe aus CuNi10Fe1Mn und CuNi3OMn1Fe [12]


Tab. 16 Dauerschwingfestigkeit verschiedener Kupfer-Nickel-Legierungen [13]

Da viele Bauteile einer schwingenden Beanspruchung unterliegen, ist auch die Dauerschwingfestigkeit, kurz Dauerfestigkeit genannt, für die Praxis eine wichtige Kenngröße. Sie ist – im Gegensatz zur Dauerstandfestigkeit – definiert als der um eine gegebene Mittelspannung schwingende größte Spannungsausschlag, den ein Werkstück (Probe) „unendlich oft“ ohne Bruch und ohne unzulässige Verformung aushält (DIN 50100).

Bei Kupferwerkstoffen existiert kein ausgeprägter Grenzwert der Spannung, sondern mit zunehmenden Lastspielzahlen wird es ein stetiger aber dann im Bereich hoher Lastspiele verschwindend geringer Abfall der Festigkeit beobachtet. Hierfür werden Zeitfestigkeiten bei hohen Lastspielen (ca. 108) als Dauerschwingfestigkeiten angegeben.

In Tab. 16 sind Werte der Dauerschwingfestigkeit von CuNi10Fe1Mn, CuNi25, CuNi39Mn1Fe und CuNi44Mn1 für eine Lastspielzahl von 108 zusammengestellt [13].


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  12. C.H. Thornton, S. Harper und J.E. Bowers: A critical survey of available high temperature mechanical property data for copper and copper alloys – Incra Monograph XII, The Metallurgy of Copper, New York 1983
  13. Copper Data Sheet No K2, K5-K7, Deutsches Kupferinstitut, Berlin 1972
  14. Metals Handbook, 9th Edition, ASM, Metals Park, Ohio 1981
  15. J.P. Chubb, J. Billingham u.a.: Effect of alloying and residual elements on strength and hot ductility of cast cupro-nickel.. J. Metals, March 1978, S. 20-25
  16. Richtwerte für die spanende Bearbeitung von Kupfer und Kupferlegierungen. Informationsdruck i. 18, Deutsches Kupferinstitut
  17. Schweißen von Kupfer und Kupferlegierungen (Fachbuch) Deutsches Kupferinstitut
  18. Guide to the welding of copper-nickel alloys. INCO Europe Ltd. 1979
  19. F. Richter und H. Lüdorff: Heißrissanfälligkeit und magnetische Permeabilität beim Werkstoff CuNi10Fe. Schweißen und Schneiden 38 (1986) 2, S. 80 ff.
  20. Normenstelle Marine – VG 81245, Teil 3 (03.91): Nichteisen-Schwermetalle; Schweißzusätze und Hartlote, Auswahl
  21. Kupfer-Nickel-Bekleidungen für Offshore-Plattformen. Sonderdruck s.202, Deutsches Kupferinstitut und Copper Development Association, 1986
  22. D.G. Melton: Review of Five-Year Exposure Data for CuNi-Sheathed Steel Pilings. OTC, Houston-Texas, May 6-9 (1991), pp 221-223