Effect of Ag content and drawing strain on microstructure and properties of directionally solidified Cu-Ag alloy

Abstract

Continuous columnar-grained Cu-Ag alloy bars containing different silver contents (6 wt%, 12 wt%, 24 wt%) with diameters of 10 mm were prepared by directional solidification technology firstly and drawn to 0.3 mm directly at room temperature without intermediate annealing in this study. With incremental Ag contents, eutectic microstructure distributed in the interdendritic region which parallel to the casting direction grew with a higher tensile strength but almost invariable elongation and electrical conductivity of the alloys. Meanwhile, the tensile strength of the alloy wires were enhanced greatly with increasing drawing strains owing to the remarkable fiber reinforcement effect, whereas the elongation and electrical conductivity decreased slowly. With the increase of drawing strains, columnar grains and eutectic phases were drawn into dense microcomposite structure, and the volume fraction of <111> texture in Cu and Ag phases increased in the three experimental alloys; while, the growth rate of <111> texture in Ag phases was lower than that in Cu phases, which is one of the main reasons for the excellent ductility of the alloys. These results may offer reference for the choice of Ag content and drawing strain, and then developing a short preparation process of Cu-Ag alloys with directional solidification + drawing (without intermediate annealing).