Influence of 0.1% Addition of Mg and/or Fe on Strength and Stress Relaxation Property of a Cu-0.52%Ni-0.19%P Alloy

Abstract

The effects of addition of 0.1 massMg and 0.1 massFe on the strength and stress relaxation property of a precipitation hardenable Cu 0.52 massNi 0.19 massP alloy aged at 450°C have been investigated. Precipitation of Ni 2 P, Ni 12 P 5 , both Ni 2 P and Ni 5 P 4 , and both Ni 12 P 5 and Ni 5 P 4 phases was observed to occur on aging the Cu Ni P, Cu Ni P Fe, Cu Ni P Mg, and Cu Ni P Fe Mg alloys, respectively. The needle like Ni 5 P 4 phase was first found to be precipitated in the Cu matrix. In the peak aging stage, the yield strength of the four alloys is controlled by the Orowan mechanism. The addition of Mg to the Cu Ni P alloy enhanced the strength of the alloy, but the Fe addition did not significantly affect the strength. The strength of the Cu Ni P Mg alloy was nearly identical to that of the Cu Ni P Fe Mg alloy. The increase in strength by the addition of Mg is ascribed to the decrease in inter precipitate spacing of precipitates. The Cu Ni P Fe alloy exhibited better stress relaxation property than the Cu Ni P alloy, probably because atoms caused by pairs of Fe and P chemical bonding are dragged by moving dislocations. Adding Mg to the Cu Ni P alloys did not essentially change the stress relaxation property. This may be as a result of the combination of the increase in stress relaxation resistance caused by the Mg atom drag effect on dislocation motion and of the decrease in that due to the decrease in the amount of P atoms in the Cu matrix by adding Mg. (Received November 5, 2009; Accepted February 9, 2010) Keywords: copper nickel phosphorus alloy, alloying element addition, Ni 2 P precipitate, Ni 12 P 5 precipitate, Ni 5 P 4 precipitate, precipitation strengthening, stress relaxation property

Effect of Co/P micro-alloying on stress relaxation behaviour of Cu-15Ni-8Sn alloy

“…Micro-alloying is an effective method for improving alloy stress relaxation resistance. According to the literature, Mg [20], Al [24], Fe [25], P [26], and Co [27] micro-alloying increased the stress relaxation resistance of copper alloys. Aruga's research [26] demonstrates that Cu-Ni-P alloys with low P content form low-density Ni-P clusters during annealing, which have a stronger pinning effect than solute atoms, resulting in a greater improvement in stress relaxation resistance compared to Cu-P alloys.…”