Changes

====5Besides the naturally hard copper materials, precipitation hardening copper alloys play also an important role as carrier materials for electrical contacts.1By means of a suitable heat treatment, finely dispersed precipitations of a second phase can be achieved, that increases the mechanical strength of these copper alloys significantly.6.1 Copper-Beryllium Alloys (Beryllium Bronze)====

The cause for precipitation hardening of CuBe materials is the rapidly diminishing solubility of beryllium in copper as temperature decrease. As thephase diagram for CuBe shows, 2.4 wt% of Be are soluble in Cu at 780°C ''(Fig. ====<!--5.28)''1. In this temperature range annealed CuBe alloys are homogeneous(solution annealing)6. The homogeneous state can be frozen through rapid cooling to room temperature 1-->Copper-Beryllium Alloys (quenchingBeryllium Bronze). 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 ''(Table 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 ''(Table 5.18)'' and ''(Figs. 5.29 - 5.31)''.====

The cause for precipitation hardening of CuBe materials, is the rapidly diminishing solubility of beryllium in copper as temperature decreases. As thephase 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_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: Phase diagram Physical_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:Mechanical Properties of copperberyllium with temperature ranges for brazing Selected Copper-Beryllium Alloys"/><!--(Table 5.18)--> and annealing treatments<xr id="fig:Precipitation_hardening_of_CuBe2_at_325°C_after_different_cold_working"/>, <xr id="fig:Precipitation_hardening_of_CuBe2_(soft)_at_325°C"/>, <xr id="fig:Precipitation_hardening_of_CuBe2_(half hard)_at_different_annealing_temperatures"/>).

As precipitation hardening alloys CuBe materials, mainly CuBe2 and CuBe1.7 have gained broad usage as current carrying contact springs because of their outstanding mechanical properties. Besides these , CuCo2Be and CuNi2Be, which have medium mechanical strength and a relatively high electricalconductivity, are also used as contact carrier materials. After stamping and forming into desired contact configurations , these CuBe materials are then precipitation hardened. CuBe alloys are available as semi-finished materials in a variety of cold work conditions. They can also be supplied and used in the already precipitation hardened condition , without significant strength losses. In this case , the hardening was already performed at the alloy producer.

Since Beryllium is rated as a carcinogen by the European regulation EU-67/548, it has been tried to reach the application properties of the well established CuBe1.7 and CuBe2 alloys with a lower Be content. The development Development efforts for alternate alternative precipitation hardening materials without toxic and declaration requiring additive materialsdeclarable additives are underway, e.g. CuNiCoSi as a substitute for example CuNiCoSi, are aimed at the replacement of CuBe.

Fig. 5.30<figure id="fig: Precipitation hardening of CuBe2 (soft) at 325°CPhase_diagram_of_copperberyllium_with_temperature_ranges_for_brazing_and_annealing_treatments">[[File:Precipitation hardening Phase diagram of CuBe2 (soft) at 325Ccopper beryllium with temperature ranges.jpg|rightleft|thumb|Precipitation hardening <caption>Phase diagram of CuBe2 (soft) at 325°Ccopper- beryllium with temperature ranges for brazing and annealing treatments</caption>]]</figure>

Fig. 5.31<figure id="fig: Precipitation hardening of CuBe2 (half hard) at different annealing temperaturesPrecipitation_hardening_of_CuBe2_at_325°C_after_different_cold_working"> [[File:Precipitation hardening of CuBe2 half hardat 325C.jpg|rightleft|thumb|<caption>Precipitation hardening of CuBe2 (half hard) at 325°C after different annealing temperaturescold working</caption>]]</figure>

'''Table 5<figure id="fig:Precipitation_hardening_of_CuBe2_(soft)_at_325°C"> [[File:Precipitation hardening of CuBe2 (soft) at 325C.17: Physical Properties jpg|left|thumb|<caption>Precipitation hardening of Selected Copper-Beryllium Alloys''' CuBe2 (2 Teile!soft)at 325°C</caption>]]</figure>

'''Table 5<figure id="fig:Precipitation_hardening_of_CuBe2_(half hard)_at_different_annealing_temperatures"> [[File:Precipitation hardening of CuBe2 half hard.18: Mechanical Properties jpg|left|thumb|<caption>Precipitation hardening of Selected Copper-Beryllium Alloys''' CuBe2 (2 Teile!half hard)at different annealing temperatures</caption>]]</figure></div><div class="clear"></div>

<figtable id====="tab:Physical_Properties_of_Selected_Copper_Beryllium_Alloys"><caption>'''<!--Table 5.1.6.2.1 17:-->Physical Properties of Selected Copper-Chromium Beryllium Alloys====='''</caption>

As the phase diagram shows, copper{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material<br />Designation<br />EN UNS !Composition<br />[wt%]!Density<br />[g/cm³]!colspan="2" style="text-align:center"|Electrical<br />Conductivity !Electrical<br />Resistivity<br />[μΩ·cm]!Thermal<br />Conductivity<br />[W/(m·K)]!Coeff. of Linear<br />Thermal<br />Expansion<br />[10^-6/K]!Modulus of<br />Elasticity<br />[GPa]!Softening Temperature<br />(approx. 10% loss in<br />strength)<br />[°C]!Melting<br />Temp Range<br />[°C]|-! !!![MS/m] ![% IACS]!!!!!!|-|CuBe1.7<br />CW100C<br />C17000|Be 1.6 - 1.8<br />Co 0.3<br />Ni 0.3<br />Cu Rest|8.4|8 - 9[[#text-chromium has reference1|^{a similar hardening profile compared to CuBe ''(Fig}]]<br />12 - 13[[#text-reference2|^b]]<br />11[[#text-reference3|^c]]|14 - 16<br />21 - 22<br />19|11 - 12. 5[[#text-reference1|^a]]<br />7.32)''7 - 8. In the hardened stage CuCr has limitations to work hardening3[[#text-reference2|^b]]9. Compared to copper it has 1[[#text-reference3|^c]]|110|17|125[[#text-reference1|^{a better temperature stability with good electrical conductivity}]]<br />[[#text-reference2|^b]]|ca. 380|890 - 1000|-|CuBe2<br />CW101C<br />C17200|Be 1.8 - 2. Hardness and electrical conductivity as 1<br />Co 0.3<br />Ni 0.3<br />Cu Rest|8.3|8 - 9[[#text-reference1|^{a function of cold working and precipitation hardening conditions are illustrated in Figs}]]<br />12 - 13[[#text-reference2|^b]]<br />11[[#text-reference3|^c]]|14 - 16<br />21 - 22<br />19|11 - 12. 5[[#text-reference1|^a]]<br />7.7 - 8.333[[#text-5reference2|^b]]<br />9.1[[#text-reference3|^c]]|110|17|125[[#text-reference1|^a]]<br />135[[#text-reference2|^b]]|ca. 380|870 - 980|-|CuCo2Be<br />CW104C<br />C17500|Co 2.0 - 2.8<br />Be 0.4 - 0.7<br />Ni 0.3<br />Cu Rest|8.8|11 - 14[[#text-reference1|^a]]<br />25 - 27[[#text-reference2|^b]]<br />27 - 34[[#text-reference3|^c]]|19 - 24<br />43 - 47<br />47 - 59|7.1 - 9.1[[#text-reference1|^a]]<br />3.7 - 4.0[[#text-reference2|^b]]<br />2.9[[#text-reference3|^c]]|210|18|131[[#text-reference1|^a]]<br />138[[#text-reference2|^b]]|ca. 450|1030 - 1070|-|CuNi2Be<br />CW110C<br />C17510|Ni 1.4 - 2.2<br />Be 0.2 - 0.6<br />Co 0.35 ''(Tables 53<br />Cu Rest|8.8|11 - 14[[#text-reference1|^a]]<br />25 - 27[[#text-reference2|^b]]<br />27 - 34[[#text-reference3|^c]]|19 - 24<br />43 - 47<br />47 - 59|7.1 - 9.1[[#text-reference1|^a]]<br />3.7 - 4.0[[#text-reference2|^b]]<br />2.9[[#text-reference3|^c]]|230|18|131[[#text-reference1|^a]]<br />138[[#text-reference2|^b]]|ca. 480|1060 - 1100|}<div id="text-reference1">_a solution annealed, and 5.20cold rolled</div><div id="text-reference2">_b solution annealed, cold rolled, and precipitation hardened</div><div id="text-reference3">_c solution annealed, cold rolled, and precipitation hardened at mill (mill hardened)''.</div></figtable><br/><br/>

<figtable id="tab:Mechanical Properties of Selected Copper-chromium materials are especially suitable for use as electrodes for resistance welding. During brazing the loss in hardness is limited if low melting brazing alloys and reasonably short heating times are usedBeryllium Alloys"><caption>'''<!--Table 5.18:-->Mechanical Properties of Selected Copper-Beryllium Alloys'''</caption>

Fig. 5.32{| class="twocolortable" style="text-align: left; font-size: Copper corner of the copper12px"|-chromium phase diagram for up !Material!Hardness<br />Condition!Tensile Strength R_m<br />[MPa]!0,2% Yield Strength<br />R_p02<br />[MPa]!Elongation<br />A₅₀<br />[%]!Vickers<br />Hardness<br />HV!Bend Radius[[#text-reference4|¹]]<br />perpendicular to <br />rolling direction!Bend Radius[[#text-reference4|¹]]<br />parallel to<br />rolling direction!Spring Bending<br />Limit σ_FB<br />[MPa]!Spring Fatigue<br />Limit σ_BW<br />[MPa]|-|CuBe1,7|R 390[[#text-reference5|^a]]<br />R 680[[#text-reference5|^a]]<br />R 1030[[#text-reference6|^b]]<br />R 1240[[#text-reference6|^b]]<br />R 680[[#text-reference7|^c]]<br />R 1100[[#text-reference7|^c]]|380 -520<br />680 - 820<br />1030 - 1240<br />1240 - 1380<br />680 - 750<br />1100 - 1200|&ge; 180<br />&ge; 600<br />&ge; 900<br />&ge; 1070<br />&ge; 480<br />&ge; 930|35<br />2<br />3<br />1<br />18<br />3|80 - 135<br />210 - 250<br />330 - 380<br />360 - 420<br />220 - 350<br />330 - 370|0x t<br />1 x t<br />1 x t<br /><br />1 x t<br />6 x t|0 x t<br />3 x t<br />1.8 wt% chromium5 x t<br /><br />1 x t<br />10 x t| <br /> <br />700<br />1000<br />390<br />790| <br /> <br />260<br />280<br /> <br />260|-|CuBe2|R 410[[#text-reference5|^a]]<br />R 690[[#text-reference5|^a]]<br />R 1140[[#text-reference6|^b]]<br />R 1310[[#text-reference6|^b]]<br />R 690[[File:Copper corner of the copper chromium phase diagram.jpg#text-reference7|^c]]<br />R 1200[[#text-reference7|^c]]|410 -540<br />690 - 820<br />1140 - 1310<br />1310 - 1480<br />690 - 760<br />1200 - 1320|right&ge; 190<br />&ge; 650<br />&ge; 1000<br />&ge; 1150<br />&ge; 480<br />&ge; 1030|thumb35<br />2<br />3<br />1<br />18<br />3|Copper corner of the copper90 -chromium phase diagram for up to 140<br />215 - 260<br />350 - 400<br />380 - 450<br />220 - 250<br />360 - 410|0 x t<br />1 x t<br /> <br /> <br />1 x t<br />5 x t|0x t<br />3 x t<br /> <br /> <br />1.8 wt% chromium5 x t<br />10 x t| <br /> <br />800<br />1040<br />400<br />900| <br /> <br />270<br />300<br /> <br />280|-|CuCo2Be<br />CuNi2Be|R 250[[#text-reference5|^a]]<br />R 550[[#text-reference5|^a]]<br />R 650[[#text-reference6|^b]]<br />R 850[[#text-reference6|^b]]<br />R 520[[#text-reference7|^c]] |250 - 380<br />550 - 700<br />650 - 820<br />850 - 1000<br />520 - 620|&ge; 140<br />&ge; 450<br />&ge; 520<br />&ge; 750<br />&ge; 340|20<br />2<br />10<br />1<br />5|60 - 90<br />160 - 200<br />195 - 230<br />240 - 290<br />150 - 180|0 x t<br />3 x t<br />1 x t<br />3 x t<br />1 x t|0 x t<br /> <br />1 x t<br />3.5 x t<br />1 x t| <br /> <br />360<br />650<br />300| <br /> <br />220<br />250<br />210|}<div id="text-reference4">₁ t: Strip thickness max. 0.5 mm</div><div id="text-reference5">_a solution annealed, and cold rolled</div><div id="text-reference6">_b solution annealed, cold rolled, and precipitation hardened</div><div id="text-reference7">_c solution annealed, cold rolled, and precipitation hardened at mill (mill hardened)</div></figtable> <br/><br/>

Fig====<!--5.1. 56.33: Softening of precipitation2--hardened and subsequently cold worked CuCr1 after 4hrs annealing>Other Precipitation Hardening Copper Alloys====

Fig. =====<!--5.34 a: Electrical conductivity of precipitation hardened CuCr 01.6 as a function of annealing conditions.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. 5.34 b: Hardness of precipitation 32)-->). In the hardened stage CuCr 0has limitations to work hardening. Compared to copper it has a better temperature stability with good electrical conductivity.6 Hardness and electrical conductivity as a function of annealing cold working and precipitation hardening conditionsare illustrated in [[#figures8|(Figs. 6 – 9]]<!--Figs. 5.33-5.35--> and <xr id="tab:Physical Properties of Other Precipitation Hardening Copper Alloys"/><!--(Tables 5.19)--> and <xr id="tab:Mechanical Properties of Other Precipitation Hardening Copper Alloys"/><!--(Tab. 5.20)-->).

FigCopper-chromium materials are especially suitable for use as electrodes for resistance welding. 5.35: Electrical conductivity During brazing the loss in hardness is limited, if low melting brazing alloys and hardness of precipitation hardened CuCr 0reasonably short heating times are used.6 after cold working

'''Table 5<figure id="fig:Copper corner of the copper-chromium phase diagram for up to 0.208 wt% chromium">[[File: Mechanical Properties Copper corner of Other Precipitation Hardening the copper chromium phase diagram.jpg|left|thumb|<caption>Copper Alloys'''corner of the copper-chromium phase diagram for up to 0.8 wt% chromium</caption>]] </figure>

<figure id=====5.1.6.2"fig:Softening of precipitation hardened and subsequently cold worked CuCr1"> [[File:Softening of precipitation hardened and subsequently cold worked CuCr1.2 Copperjpg|left|thumb|<caption>Softening of precipitation-Zirconium Alloys=====hardened and subsequently cold worked CuCr1 after 4hrs annealing</caption>]]</figure>

The solubility <figure id="fig:Electrical conductivity of Zirconium in copper is precipitation hardened CuCr 0.15 wt% Zr at the eutectic temperature 6"> [[File:Electrical conductivity of 980°C ''(Figprecipitation hardened CuCr 0. 56.36)''jpg|left|thumb|<caption>Electrical conductivity of precipitation hardened CuCr 0. Copper-zirconium materials have 6 as a similar properties spectrum compared to the one for copper-chromium materials. At room temperature the mechanical properties function of copper-zirconium are less suitable than those of copper chromium, its temperature stability is however at least the same.annealing conditions</caption>]]</figure>

<figure id=====5"fig:Hardness of precipitation hardened CuCr 0.16"> [[File:Hardness of precipitation hardened CuCr 0.6.2jpg|left|thumb|<caption>Hardness of precipitation hardened CuCr 0.3 Copper-Chromium-Zirconium Alloys=====6 as a function of annealing conditions</caption>]]</figure>

The earlier used <figure id="fig:Electrical conductivity and hardness of precipitation hardened CuCr and CuZr materials have been partially replaced over the years by the capitation hardening three materials alloy CuCr1Zr0. This material exhibits high mechanical strength at elevated temperatures 6"> [[File:Electrical conductivity and good oxidation resistance as well as high softening temperatures. In its hardness of precipitation hardened condition CuCr1Zr has also a high electrical conductivity (Bild 5CuCr 0.37)6. Their usage extends from mechanically jpg|left|thumb|<caption>Electrical conductivity and thermally highly stressed parts such as contact tulips in high voltage switchgear to electrodes for resistance weldinghardness of precipitation hardened CuCr 0.6 after cold working</caption>]]</figure></div><div class="clear"></div>

<figtable id="tab:Physical Properties of Other Precipitation Hardening Copper Alloys"><caption>'''<!--Table 5.19:-->Physical Properties of Other Precipitation Hardening Copper Alloys'''</caption>  {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material<br />Designation<br />EN UNS !Composition<br />[wt%]!Density<br />[g/cm³]!colspan="2" style="text-align:center"|Electrical<br />Conductivity !Electrical<br />Resistivity<br />[μΩ·cm]!Thermal<br />Conductivity<br />[W/(m·K)]!Coeff. of Linear<br />Thermal<br />Expansion<br />[10^-6/K]!Modulus of<br />Elasticity<br />[GPa]!Softening Temperature<br />(approx. 10% loss in<br />strength)<br />[°C]!Melting<br />Temp Range<br />[°C]|-!!!![MS/m] ![% IACS]!!!!!!|-|CuCr|Cr 0.3 - 1.2<br />Cu Rest|8.89|26[[#text-reference8|^a]]<br />48[[#text-reference9|^b]]|45[[#text-reference8|^a]]<br />83[[#text-reference9|^b]]|3.8[[#text-reference8|^a]]<br />2.1[[#text-reference9|^b]]|170[[#text-reference8|^a]]<br />315[[#text-reference9|^b]]|17|112|ca. 450|980 - 1080|-|CuZr|Zr 0.1 - 0.3<br />Cu Rest|8.9|35[[#text-reference8|^a]]<br />52[[#text-reference9|^b]]|60[[#text-reference8|^a]]<br />90[[#text-reference9|^b]]|2.9[[#text-reference8|^a]]<br />1.9[[#text-reference9|^b]]|340[[#text-reference8|^a]]|16|135|ca. 500|1020 - 1080|-|CuCr1Zr<br />CW106C<br />C18150|Cr 0.5 - 1.2<br />Zr 0.03 - 0.3<br />Cu Rest|8.92|20[[#text-reference8|^a]]<br />43[[#text-reference9|^b]]|34[[#text-reference8|^a]]<br />74[[#text-reference9|^b]]|5.0[[#text-reference8|^a]]<br />2.3[[#text-reference9|^b]]|170[[#text-reference8|^a]]<br />310 - 330[[#text-reference9|^b]]|16|110[[#text-reference8|^a]]<br />130[[#text-reference9|^b]]|ca. 500|1070 - 1080|}<div id="text-reference8">_a solution annealed, and cold rolled</div><div id="text-reference9">_b solution annealed, cold rolled, and precipitation hardened</div></figtable><br /><br /> <figtable id="tab:Mechanical Properties of Other Precipitation Hardening Copper Alloys"><caption>'''<!--Table 5.20:-->Mechanical Properties of Other Precipitation Hardening Copper Alloys'''</caption> <table class="twocolortable"><tr><th><p class="s16">Material</p></th><th><p class="s16">Hardness</p><p class="s16">Condi- tion</p></th><th><p class="s16">Tensile</p><p class="s16">Strength R<span class="s18">m</span></p><p class="s16">[MPa]</p></th><th><p class="s16">0,2% Yield</p><p class="s16">Strength R<span class="s18">p02</span></p><p class="s16">[MPa]</p></th><th><p class="s16">Elongation</p><p class="s16">A50</p><p class="s16">[%]</p></th><th><p class="s16">Vickers</p><p class="s16">Hardness</p><p class="s16">HV</p></th><th><p class="s16">Spring Bending</p><p class="s16">Limit <span class="s19">F</span><span class="s18">FB </span>[MPa]</p></th></tr><tr><td><p class="s16">CuCr</p></td><td><p class="s16">R 230<span class="s18">a</span></p><p class="s16">R 400<span class="s18">a </span>R 450<span class="s18">b </span>R 550<span class="s18">b</span></p></td><td><p class="s33">&gt;<span class="s16"> 230</span></p><p class="s33">&gt;<span class="s16"> 400</span></p><p class="s33">&gt;<span class="s16"> 450</span></p><p class="s33">&gt;<span class="s16"> 550</span></p></td><td><p class="s33">&gt;<span class="s16"> 80</span></p><p class="s33">&gt;<span class="s16"> 295</span></p><p class="s33">&gt;<span class="s16"> 325</span></p><p class="s33">&gt;<span class="s16"> 440</span></p></td><td><p class="s16">30</p><p class="s16">10</p><p class="s16">10</p><p class="s16">8</p></td><td><p class="s33">&gt;<span class="s16"> 55</span></p><p class="s33">&gt;<span class="s16"> 120</span></p><p class="s33">&gt;<span class="s16"> 130</span></p><p class="s33">&gt;<span class="s16"> 150</span></p></td><td><p class="s16">350</p></td></tr><tr><td><p class="s16">CuZr</p></td><td><p class="s16">R 260<span class="s18">a</span></p><p class="s16">R 370<span class="s18">a </span>R 400<span class="s18">b </span>R 420<span class="s18">b</span></p></td><td><p class="s33">&gt;<span class="s16"> 260</span></p><p class="s33">&gt;<span class="s16"> 370</span></p><p class="s33">&gt;<span class="s16"> 400</span></p><p class="s33">&gt;<span class="s16"> 420</span></p></td><td><p class="s33">&gt;<span class="s16"> 100</span></p><p class="s33">&gt;<span class="s16"> 270</span></p><p class="s33">&gt;<span class="s16"> 280</span></p><p class="s33">&gt;<span class="s16"> 400</span></p></td><td><p class="s16">35</p><p class="s16">12</p><p class="s16">12</p><p class="s16">10</p></td><td><p class="s33">&gt;<span class="s16"> 55</span></p><p class="s33">&gt;<span class="s16"> 100</span></p><p class="s33">&gt;<span class="s16"> 105</span></p><p class="s33">&gt;<span class="s16"> 115</span></p></td><td><p class="s16">280</p></td></tr><tr><td><p class="s16">CuCr1Zr</p></td><td><p class="s16">R 200<span class="s18">a</span></p><p class="s16">R 400<span class="s18">b</span></p><p class="s16">R 450<span class="s18">b</span></p></td><td><p class="s33">&gt;<span class="s16"> 200</span></p><p class="s33">&gt;<span class="s16"> 400</span></p><p class="s33">&gt;<span class="s16"> 450</span></p></td><td><p class="s33">&gt;<span class="s16"> 60</span></p><p class="s33">&gt;<span class="s16"> 210</span></p><p class="s33">&gt;<span class="s16"> 360</span></p></td><td><p class="s16">30</p><p class="s16">12</p><p class="s16">10</p></td><td><p class="s33">&gt;<span class="s16"> 70</span></p><p class="s33">&gt;<span class="s16"> 140</span></p><p class="s33">&gt;<span class="s16"> 155</span></p></td><td><p class="s16">420</p></td></tr></table></figtable> =====<!--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 or electrodes for resistance welding. <div class="multiple-images"><figure id="fig:Copper corner of the copper zirconium for up to 0.5-wt zirconium">[[File:Copper corner of the copper zirconium for up to 0.5-wt zirconium.jpg|right|thumb|Figure 10: Copper corner of the copper- zirconium for up to 0.5 wt% zirconium]] </figure> <figure id="fig:Softening of CuCr1Zr after1hr annealing">[[File:Softening of CuCr1Zr after 1hr annealing.jpg|right|thumb|Figure 11: Softening of CuCr1Zr after 1 hr annealing and after 90%cold working]]</figure></div><div class="clear"></div>