The softening temperature of copper can be increased through the addition of certain alloying elements such as silver or zircon (Figure 2) without seriously compromising the alloy's conductivity (Figure 3). This is a great advantage in many electrical application, such as in current-carrying parts that are exposed to higher temperatures or mechanical stresses in that they are not softened and misshapened (commutator, armature windings, etc.).
Kupfer-Silber bildet ein eutektisches System mit einer maximalen Löslichkeit von 8 % Silber bei der eutektischen Temperatur von 779°C.
Copper-silver alloys, with a maximum silver content of 8%, create an eutectic system at (or with) an eutectic temperature of 779°C.
These common commercial alloys contain between 0.03% and 0.12% Ag and have a single-phase structure. Within this range, the silver serves to increase the softening temperature. The standards DIN EN 1976 and DIN EN 1977 contain copper-silver alloys with varying silver content and are further differentiate by oxygen-containing, oxygen-free or phosphorus oxidized copper.
Compared to pure copper, copper-silver alloys have another advantage. Strain hardening accomplished through cold forming remains intact even at relatively high temperatures. The softening temperature of CuAg0.10 is approximately 300°C. Another excellent feature of copper-silver alloys is the relatively high creep strength , which is particularily useful under strain at high temperatures. Electrical and thermal conductivity are not greatly influenced by the addition of silver (Figure 3).
At 972°C, zircon is approximately 0.17% soluable in copper . Because soluability decreases with sinking temperatures, the alloys are curable. Only one alloy with 0.1% Zr is listed in DIN CEN/TS 13388. CuZr is oxygen free and thus not sensitive to hydrogen embrittlement.
CuZr has both a high conductivity of approximately 54 MS/m (95% IACS) and a hardness value of up to 480 MPa. This combination is uncommon when compared to other low-alloy coppers. Additionally, the material has a very high softening temperature which is adventageous soldering (Figure 5).
The actual curing effect is relatively minimal and therefore only brings technological benefits when combined with strain hardening. Thus, for practical applications, the material is generally heat treated, cold worked and then hardened or is first hardened, and then cold formed. The effects of curing begin to drop at temperatures above 525 ° C. After annealing, for example about 1 hour at 425 ° C, the alloys remains solid. Also notable, is the increased creep strength of copper-zircon alloys, even at significantly higher temperatures.