COPPER-NICKEL-SILICON-CHROMIUM ALLOY HAVING IMPROVED ELECTRICAL CONDUCTIVITY

摘要

A copper-nickel-silicon-chromium alloy having a high hardness and improved electrical conductivity. The alloy is composed by weight of 2.0% to 3.0% nickel, 0.4% to 0.5% silicon, 0.1% to 0.5% chromium, and the balance copper. The silicon is used in excess of the stoichiometric relationship wtih nickel to provide excess silicon, and the chromium is used in excess of the stoichiometric relationship with the excess silicon. The alloy is heat treated by initially heating the alloy to a temperature in the range of 1600.degree.F to 1800.degree.F and is thereafter quenched. The quenched alloy is then subjected to a two-step aging treatment in which the alloy is initially aged at a temperature of 482.degree.C to 593.degree.C to precipitate the metal silicides and develop a hardness in excess of 90 Rockwell B (185 Brinell) and subsequently is subjected to a second aging at a temperature in the range of 399.degree.C to 482.degree.C, which serves to precipitate the excess chromium from solution and increase the electrical conductivity to a value greater than 45%.