Cu-Ni-Sn-P合金の応力緩和特性の解明

Abstract

The effects of alloying elements on the stress relaxation property of Cu-Ni-Sn-P alloys have been investigated using Cu, Cu-1.5 at% (1.4 mass%) Ni alloys, Cu-0.75 at% (0.7 mass%) Ni-0.75 at% (1.4 mass%) Sn alloys and Cu-1.5 at% (2.8 mass%) Sn alloys with and without 0.14 at% (0.07 mass%) P. Adding Sn to Cu enhances the resistance to stress relaxation by dragging atmospheres of Sn atoms behind dislocations. The Cu-Ni-P alloy exhibits better stress relaxation property than the Cu-Ni and Cu-P alloys, probably because atoms caused by pairs of P and Ni chemical binding are dragged by moving dislocations. Annealing of the Cu alloys with P at a low temperature of 300°C for a short time brings about higher stress-relaxation resistance. This is ascribed to the decrease in mobile dislocation density by segregation of P atoms on dislocations during the annealing. Adding 0.1 at% (0.04 mass%) Mg to the Cu-Ni-Sn-P alloy decreases the amounts of Ni and P dissolved in the Cu matrix, resulting in lower stress-relaxation resistance. The addition of 0.1 at% (0.09 mass%) Fe to the Cu-Ni-Sn-P alloy is effective for the improvement of stress relaxation property.