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→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 ''(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 ''(Figs. 5.29 - 5.31)''.
Fig. 5.28:Phase diagram of copperberylliumwith temperature ranges for brazing and annealing treatments [[File:Phase diagram of copper beryllium with temperature ranges.jpg|right|thumb|Phase diagram of copper- beryllium with temperature ranges forbrazing and annealing treatments]]
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 electrical
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.
Fig. 5.29:Precipitation hardeningof CuBe2 at 325°C afterdifferent cold working
Fig. 5.30:Precipitationhardening of CuBe2(soft) at 325°C
Fig. 5.31:Precipitationhardening of CuBe2(half hard) at differentannealing temperatures
Table 5.17: Physical Properties of Selected Copper-Beryllium Alloys (2 Teile!)
