Improvement of elevated temperature mechanical properties of Cu–Ni–Sn–Pb alloys

Cu–Ni–Sn alloys with Pb additions exhibit high mechanical strength at room temperature coupled with good machinability but experience a significant ductility loss above the melting point of lead. We explore here the influence of minor additions of Al, Mn, Zr, B or P to the copper alloy CuNi9Sn6Pb1 on its tensile properties at 400 °C and 10 −2 s −1. Only boron and phosphorous additions have a clear beneficial effect. Unlike other elements tested, these form intermetallic particles; it is proposed that the improvement results from a combination of capillary pinning and mechanical shielding by these particles of the molten lead inclusions in the alloy.