Solute effects in very dilute ternary CuMnSe alloys

Abstract

To understand the nature of the interactions between copper and controlled parts-per-million additions of manganese and selenium in promoting the softening resistance of high purity oxygen-free coppers, recrystallization studies coupled with resistivity ratio measurements were conducted. Microstructural changes and the nature of precipitation and segregation in this alloy system were also studied employing transmission and scanning electron microscopy techniques. Maximum enhancement in the softening temperature relative to 99.999+% copper was 250 K, and this occurred at a selenium-to-manganese molar ratio of about unity. The room temperature electrical conductivities of alloys containing less than 100 ppm of total solute additions were typically 100% with respect to the International Annealed Copper Standard. Microscopic investigation indicated grain refinement, increased twin density and evidence for precipitation of compounds as well as elemental segregation. The results were interpreted employing models for precipitation kinetics, solubility effects and segregation phenomena. The addition of two or more elements to copper offers possibilities for property improvement through binary and ternary interactions and reactions. The concept of alloying strong surface segregants (e.g. selenium, tellurium and sulfur) with metals soluble in copper (e.g. manganese and nickel) appears to be potentially useful in designing alloys which simultaneously possess a high electrical conductivity and a high softening temperature.