Enhancing mechanical and electrical properties of the Cu-0.2Be-1.0Ni alloy via dual plastic deformations

Despite the excellent electrical and thermal conductivities of low-beryllium copper alloys, the limited mechanical properties severely impede their widespread applications. Here, dual plastic deformation treatments via rolling and ultrasonic surface modification are conducted to the matrix and surface of the Cu-0.2Be-1.0Ni alloy, followed by aging. It is found that, the large plastic deformation is introduced into the alloy and especially a 200 μm deep gradient deformation layer from the interior to surface can be observed with gradually refined grains, increasing dislocation density and decreasing precipitates. These microstructural characteristics confer the alloy a high tensile strength of 894.7 MPa, elongation of 18.3 % and electrical conductivity of 60.1 % IACS. Analyses reveal that, in the alloy interior, the large plastic deformation promotes the generation of dense and coherent precipitates, fundamentally contributing to the high strength and electrical conductivity. Concurrently, in the alloy surface layer, the greatly refined grains mitigate stress concentration and the gradient heterostructures suppress microcrack propagation, which further improve the alloy strength and elongation. This work may provide an alternative approach to alleviate the enduring trade-off between strength and conductivity in copper alloys.