Copper and nickel are in their solid and liquid phase completely soluble in each other (<xr id="fig:Phase_diagram_of_copper-nickel_for_the_range_of_0-50_wt_nickel"/><!--(Fig. 5.21)-->). Because of their very low electrical conductivity they are mainly used as resistance alloys <xr id="fig:Electrical_conductivity_of_copper-nickel_alloys_as_a_function_of_nickel_content"/><!--(Fig. 5.22)-->. The work hardening and softening behavior of CuNi alloys and CuNi9Sn2 are shown in [[#figures6|(Figs. 3 – 7)]]<!--(Figs. 5.23 – 5.27)-->. Coppernickel alloys exhibit high corrosion resistance, good weldabilty, and the suitability for cladding to other materials. Because of these and their other properties <xr id="tab:Physical_ Properties_of_Selected_Copper_Nickel_Alloys"/><!--(Tab. 5.15)--> and <xr id="tab:Mechanical_Properties_of_Selected_Copper_Nickel_Alloys"/><!--(Tab. 5.16)--> they are, with and without additives of iron or manganese, widely used as good weldable backing layers on weld buttons and weld profiles (weld tapes).