Microstructure evolution, precipitation behavior, and mechanical properties of continuously extruded Cu-Ni-Si alloys at different aging treatments

A route for increasing the mechanical and electrical properties of Cu-Ni-Si alloys was proposed in the present study. Microstructure evolution and precipitation behavior were investigated in each process to tune the final properties. The results showed that dynamic recrystallization and dynamic precipitation occur partially during continuous extrusion, increasing the mechanical and electrical properties of the Cu-Ni-Si alloy. The properties were further improved by subsequent aging via different mechanisms. Aging at 400 C or 600 C can lead to either massive residual dislocations or early nascent precipitates in the matrix, which causes a limited increase in either electrical conductivity or mechanical strength. The properties can be compensated by eliminating dislo-cations and increasing the number of ripe Ni2Si precipitates at medium aging temperatures. The microstructure under these conditions, however, is not homogeneous at the edge and center areas and, the texture evolution highly depends on the aging temperature and local plastic deformation imposed. A nearly recrystallized structure possessing fine grain size and massive precipitates was achieved after an additional aging-rolling-aging process which also changes the deformed Cube {001}(100 > and R{111} < 211 > textures to recrystallized Brass {110}( 112 > texture. The tensile strength and electrical conductivity then increase from 612 MPa to 763 MPa and 36.1 % IACS to 49.6 % IACS, respectively. The present results thus provide a new route and some valuable insights to manufacture high-strength and high electrical conductivity Cu-Ni-Si alloys in production.