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 , that increases the mechanical strength of these copper alloys significantly.

The cause for precipitation hardening of CuBe materials , is the rapidly diminishing solubility of beryllium in copper as temperature decreasedecreases. 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: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 Selected Copper-Beryllium Alloys"/><!--(Table 5.18)--> and [[#figures7|(Figs. 43 – 75)]]<!--(Figs. 5.29 - 5.31)-->).