Copper alloy and process for producing the same

A copper alloy comprising:

• at least two elements selected from the group consisting of 0.01 to 5% Cr, 0.01 to 5% Ti and 0.01 to 5% Zr;
• 5% or less in total of one or more elements selected from the following groups (b), (c) and (d):
• group (b):
• 0.001 to 0.5% each of P, S, As, Pb and B;
• group (c):
• 0.01 to 5% each of Sn, Mn, Fe, Co, Al, Si, Nb, Ta, Mo, V, W and Ge;
• group (d):
• 0.01 to 3% each of Zn, Ni, Te, Cd and Se;
• and the balance Cu and impurities,
• wherein the relationship between the total number N and the diameter X satisfies the following formula (1):
• log N≦0.4742+17.629×exp(−0.1133×X) (1)
• wherein N means the total number of precipitates and intermetallics, having a diameter of not smaller than 1 μm which are found in 1 mm2 of the alloy;
• and X means the diameter in μm of the precipitates and the intermetallics having a diameter of not smaller than 1 μm.

A copper alloy comprising:

• at least two elements selected from the group consisting of 0.01 to 5% Cr, 0.01 to 5% Ti and 0.01 to 5% Zr;
• 0.001 to 2% in total of one or more elements selected from the following group (e):
• group (e):
• Mg, Li, Ca and rare earth elements;
• and the balance Cu and impurities,
• wherein the relationship between the total number N and the diameter X satisfies the following formula (1):
• log N≦0.4742+17.629×exp(−0.1133×X) (1)
• wherein N means the total number of precipitates and intermetallics, having a diameter of not smaller than 1 μm which are found in 1 mm2 of the alloy;
• and X means the diameter in μm of the precipitates and the intermetallics having a diameter of not smaller than 1 μm.

A copper alloy comprising:

• at least two elements selected from the group consisting of 0.01 to 5% Cr, 0.01 to 5% Ti and 0.01 to 5% Zr;
• 0.001 to 0.3% in total of one or more elements selected from the following group (f):
• group (f):
• Bi, Tl, Rb, Cs, Sr, Ba, Tc, Re, Os, Rh, In, Pd, Po, Sb, Hf, Au, Pt and Ga;
• and the balance Cu and impurities,
• wherein the relationship between the total number N and the diameter X satisfies the following formula (1):
• log N≦0.4742+17.629×exp(−0.1133×X) (1)
• wherein N means the total number of precipitates and intermetallics, having a diameter of not smaller than 1 μm which are found in 1 mm2 of the alloy;
• and X means the diameter in μm of the precipitates and the intermetallics having a diameter of not smaller than 1 μm.