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→5.1.6.1 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 the
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 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 ''(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 ''[[#figures7|(Figs. 43 – 75)]](Figs. 5.29 - 5.31)''.
<figure id="fig:Phase diagram of copperberyllium with temperature ranges for brazing and annealing treatments">
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 efforts for alternate precipitation hardening materials without toxic and declaration requiring additive materials, for example CuNiCoSi, are aimed at the replacement of CuBe.
<div id="figures7"><xr id="fig:Precipitation 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 (soft) at 325°C"/> Fig. 5.30: Precipitation hardening of CuBe2 (soft) at 325°C <xr id="fig:Precipitation hardening of CuBe2 (half hard) at different annealing temperatures"/> Fig. 5.31: Precipitation hardening of CuBe2 (half hard) at different annealing temperatures</div> <div class="multiple-images"><figure id="fig:Precipitation hardening of CuBe2 at 325°C after different cold working">
[[File:Precipitation hardening of CuBe2 at 325C.jpg|right|thumb|Precipitation hardening of CuBe2 at 325°C after different cold working]]
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[[File:Precipitation hardening of CuBe2 (soft) at 325C.jpg|right|thumb|Precipitation hardening of CuBe2 (soft) at 325°C]]
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[[File:Precipitation hardening of CuBe2 half hard.jpg|right|thumb|Precipitation hardening of CuBe2 (half hard) at different annealing temperatures]]
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'''Table 5.17: Physical Properties of Selected Copper-Beryllium Alloys''' (2 Teile!)
