Stress relaxation-influence of composition and conductivity

Stress relaxation measured at different temperatures up to 175°C for two alloys is discussed. One is conventional phosphor bronze CuSn4 (C511), and the other is a recently developed alloy with nickel addition and lower tin content (CuNi1.7Sn1.2). The CuNiSn alloy has higher modulus of elasticity and higher electrical conductivity. The relaxation tests show that it has better properties, especially at high temperatures. Stress relaxation is very much influenced by the temperature. In an actual connector the temperature rise depends among other things on the conductivity of the material. Connectors of equal design but made of different material therefore reach different temperatures at a certain current. Theoretical calculations of the temperature rise at different current intensities have been performed. When the relaxation data are plotted against current intensities, alloys with higher conductivity reach lower temperatures and therefore show better relaxation properties