Copper alloy having high strength, high electric conductivity and excellent bending workability

A copper alloy, comprising, in terms of mass %, 0.4 to 4.0% of Ni;

• 0.05 to 1.0% of Si;
• and, as an element M, 0.005 to 1.0% of Cr, with the remainder being copper and inevitable impurities, and having a microstructure as treated by solution treatment temperature up to 400° C. at a rate of 5 to 100° C./hour,
• an atom number ratio M/Si of elements M and Si in a precipitate having a size of 50 to 200 nm in a microstructure of the copper alloy is from 0.01 to 10 on average, the atom number ratio being measured by a field emission transmission electron microscope with a magnification of 30,000 and an energy dispersive analyzer,
• a number density of the precipitate having a size of 50 to 200 nm in the microstructure of the copper alloy is from 0.2 to 20 per μm2 on average, the number density being measured by the field emission transmission electron microscope and the energy dispersive analyzer,
• an average atom concentration of P contained in the precipitate having said size is from 0.1 to 80 at %,
• an average grain size represented by (Σx)/n is 30 μm or less, wherein n represents a number of grains and x represents a size of each of the grains, respectively, according to a measurement by a crystal orientation analysis method using a field emission scanning electron microscope and a backscattered electron diffraction image system mounted thereon,
• a 0.2% proof strength of at least 800 mPa, and
• an electrical conductivity of at least 40% IACS.