Mechanical Properties and Fracture Behavior of Cu-Co-Be Alloy after Plastic Deformation and Heat Treatment

Abstract

Mechanical properties and fracture behavior of Cu-0. 84Co-0. 23Be alloy after plastic deformation and heat treatment were comparatively investigated. Severe plastic deformation by hot extrusion and cold drawing was adopted to induce large plastic strain of Cu-0. 84Co-0. 23Be alloy. The tensile strength and elongation are up to 476. 6 MPa and 18%, respectively. The fractured surface consists of deep dimples and micro-voids. Due to the formation of supersaturated solid solution on the Cu matrix by solution treatment at 950 °C for 1 h, the tensile strength decreased to 271. 9 MPa, while the elongation increased to 42%. The fracture morphology is parabolic dimple. Furthermore, the tensile strength increased significantly to 580. 2 MPa after aging at 480 °C for 4 h. During the aging process, a large number of precipitates formed and distributed on the Cu matrix. The fracture feature of aged specimens with low elongation (4. 6%) exhibits an obvious brittle intergranular fracture. It is confirmed that the mechanical properties and fracture behavior are dominated by the microstructure characteristics of Cu-0. 84Co-0. 23Be alloy after plastic deformation and heat treatment. In addition, the fracture behavior at 450 °C of aged Cu-0. 84Co-0. 23Be alloy was also studied. The tensile strength and elongation are 383. 6 MPa and 11.2%, respectively. The fractured morphologies are mainly candy-shaped with partial parabolic dimples and equiaxed dimples. The fracture mode is multi-mixed mechanism that brittle intergranular fracture plays a dominant role and ductile fracture is secondary.