Changes

Besides the naturally hard copper materials precipitation hardening copper alloys play also an important role as carrier materials for electrical contacts. By means of a suitable heat treatment finely dispersed precipitations of a second phase can be achieved which increase the mechanical strength of these copper alloys significantly.  ====<!--5.1.6.1 -->Copper-Beryllium Alloys (Beryllium Bronze)====

phase diagram for CuBe shows, 2.4 wt% of Be are soluble in Cu at 780°C <xr id="fig:Phase diagram of copperberyllium with temperature ranges for brazing and annealing treatmentsPhase_diagram_of_copperberyllium_with_temperature_ranges_for_brazing_and_annealing_treatments"/> <!--(Fig. 5.28)-->. In this temperature range annealed CuBe alloys are homogeneous(solution annealing). The homogeneous state can be frozen through rapid cooling to room temperature (quenching). Through a subsequent annealing at 325°C the desired precipitation hardening is achieved which results in a significant increase in mechanical strength and electrical conductivity of CuBe <xr id="tab:tab5.17Physical_Properties_of_Selected_Copper_Beryllium_Alloys"/> <!--(Tab. 5.17)-->. The final strength and hardness values depend on the annealing temperature and time as well as on the initial degree of cold working <xr id="tab:tab5.18Mechanical Properties of Selected Copper-Beryllium Alloys"/> <!--(Table 5.18) --> and [[#figures7|(Figs. 43 – 75)]]<!--(Figs. 5.29 - 5.31)-->.

<xr id="fig:Phase diagram of copperberyllium with temperature ranges for brazing and annealing treatmentsPhase_diagram_of_copperberyllium_with_temperature_ranges_for_brazing_and_annealing_treatments"/> <!--Fig. 5.28: --> Phase diagram of copper- beryllium with temperature ranges for brazing and annealing treatments

<xr id="fig:Precipitation hardening of CuBe2 at 325°C after different cold workingPrecipitation_hardening_of_CuBe2_at_325°C_after_different_cold_working"/> <!--Fig. 5.29: --> Precipitation hardening of CuBe2 at 325°C after different cold working

<xr id="fig:Precipitation hardening of CuBe2 Precipitation_hardening_of_CuBe2_(soft) at 325°C_at_325°C"/> <!--Fig. 5.30: --> Precipitation hardening of CuBe2 (soft) at 325°C

<xr id="fig:Precipitation hardening of CuBe2 Precipitation_hardening_of_CuBe2_(half hard) at different annealing temperatures_at_different_annealing_temperatures"/> <!--Fig. 5.31: --> Precipitation hardening of CuBe2 (half hard) at different annealing temperatures

<figure id="fig:Phase diagram of copperberyllium with temperature ranges for brazing and annealing treatmentsPhase_diagram_of_copperberyllium_with_temperature_ranges_for_brazing_and_annealing_treatments">

<figure id="fig:Precipitation hardening of CuBe2 at 325°C after different cold workingPrecipitation_hardening_of_CuBe2_at_325°C_after_different_cold_working">

<figure id="fig:Precipitation hardening of CuBe2 Precipitation_hardening_of_CuBe2_(soft) at 325°C_at_325°C">

<figure id="fig:Precipitation hardening of CuBe2 Precipitation_hardening_of_CuBe2_(half hard) at different annealing temperatures_at_different_annealing_temperatures">

 <figtable id="tab:tab5.17Physical_Properties_of_Selected_Copper_Beryllium_Alloys"><caption>'''<!--Table 5.17: -->Physical Properties of Selected Copper-Beryllium Alloys''' </caption>

<figtable id="tab:tab5.18Mechanical Properties of Selected Copper-Beryllium Alloys"><caption>'''<!--Table 5.18: -->Mechanical Properties of Selected Copper-Beryllium Alloys''' </caption>

====<!--5.1.6.2 -->Other Precipitation Hardening Copper Alloys====

=====<!--5.1.6.2.1 -->Copper-Chromium Alloys=====

As the phase diagram shows, copper-chromium has a similar hardening profile compared to CuBe <xr id="fig:Copper corner of the copper-chromium phase diagram for up to 0.8 wt% chromium"/><!--(Fig. 5.32)-->. In the hardened stage CuCr has limitations to work hardening. Compared to copper it has a better temperature stability with good electrical conductivity. Hardness and electrical conductivity as a function of cold working and precipitation hardening conditions are illustrated in [[#figures8|(Figs. 6 – 9)]] <!--Figs. 5.33-5.35-->, <xr id="tab:tab5.19Physical Properties of Other Precipitation Hardening Copper Alloys"/> <!--(Tables 5.19) --> and <xr id="tab:tab5.20Mechanical Properties of Other Precipitation Hardening Copper Alloys"/> <!--(Tab. 5.20)-->.

<xr id="fig:Copper corner of the copper-chromium phase diagram for up to 0.8 wt% chromium"/> <!--Fig. 5.32: --> Copper corner of the copper-chromium phase diagram for up to 0.8 wt% chromium

<xr id="fig:Softening of precipitation hardened and subsequently cold worked CuCr1"/> <!--Fig. 5.33: --> Softening of precipitation-hardened and subsequently cold worked CuCr1 after 4hrs annealing

<xr id="fig:Electrical conductivity of precipitation hardened CuCr 0.6"/> <!--Fig. 5.34 a: --> Electrical conductivity of precipitation hardened CuCr 0.6 as a function of annealing conditions

<xr id="fig:Hardness of precipitation hardened CuCr 0.6"/> <!--Fig. 5.34 b: --> Hardness of precipitation hardened CuCr 0.6 as a function of annealing conditions

<xr id="fig:Electrical conductivity and hardness of precipitation hardened CuCr 0.6"/> <!--Fig. 5.35: --> Electrical conductivity and hardness of precipitation hardened CuCr 0.6 after cold working

 <figtable id="tab:tab5.19Physical Properties of Other Precipitation Hardening Copper Alloys"><caption>'''<!--Table 5.19: -->Physical Properties of Other Precipitation Hardening Copper Alloys''' </caption>

 <figtable id="tab:tab5.20Mechanical Properties of Other Precipitation Hardening Copper Alloys"><caption>'''<!--Table 5.20: -->Mechanical Properties of Other Precipitation Hardening Copper Alloys'''</caption>

=====<!--5.1.6.2.2 -->Copper-Zirconium Alloys=====

The solubility of Zirconium in copper is 0.15 wt% Zr at the eutectic temperature of 980°C <xr id="fig:Copper corner of the copper zirconium for up to 0.5-wt zirconium"/> <!--(Fig. 5.36)-->. Copper-zirconium materials have a similar properties spectrum compared to the one for copper-chromium materials. At room temperature the mechanical properties of copper-zirconium are less suitable than those of copper chromium, its temperature stability is however at least the same.

=====<!--5.1.6.2.3 -->Copper-Chromium-Zirconium Alloys=====

The earlier used CuCr and CuZr materials have been partially replaced over the years by the capitation hardening three materials alloy CuCr1Zr. This material exhibits high mechanical strength at elevated temperatures and good oxidation resistance as well as high softening temperatures. In its hardened condition CuCr1Zr has also a high electrical conductivity <xr id="fig:Softening of CuCr1Zr after 1hr annealing"/> <!--(Bild 5.37)-->. Their usage extends from mechanically and thermally highly stressed parts such as contact tulips in high voltage switchgear to electrodes for resistance welding.

<xr id="fig:Copper corner of the copper zirconium for up to 0.5-wt zirconium"/> <!--Fig. 5.36: --> Copper corner of the copper- zirconium for up to 0.5 wt% zirconium)

<xr id="fig:Softening of CuCr1Zr after 1hr annealing"/> <!--Fig. 5.37: --> Softening of CuCr1Zr after 1 hr annealing and after 90% cold working)