Mechanisms of primary phase refinement and toughness improvement of Cu–2 wt% Ag–0.15 wt% La alloy through continuous extrusion forming

Abstract

A new Cu–2 wt% Ag–0.15 wt% La alloy composed of large-size Ag-rich primary phases was processed into wire billets by successive drawing, annealing and continuous extrusion forming (CONFORM). The microstructural evolution and mechanical properties of the samples obtained by drawing, annealing and CONFORM were then investigated. The results indicate that a desirable combination of high ultimate tensile strength (300 MPa) and elongation (49.5%) was obtained after CONFORM. The latter allowed the microstructure to be significantly refined via an almost full dynamic recrystallization (DRX), with grain sizes of ~ 1 μm. In addition, the large-size primary phases were broken into dispersed nanophases with an average size of 800 nm. The dispersed phases promoted the DRX of the matrix via particle-stimulated nucleation. As a result, the enhanced toughness (11145.98 MPa·%) is contributed by grain refinement and dispersion strengthening of the nanosized phases.