黄铜包纯铜绞线复合材料拉拔过程中横截面结构、显微组织和力学性能变化

Cross-sectional structure, microstructure and mechanical property evolutions of brass cladding pure copper stranded wire composite during drawing

对采用固/液连铸复合成形工艺制备的外径8.5 mm黄铜包覆纯铜绞线复合坯进行拉拔加工,研究拉拔过程中复合材料横截面结构、组织和力学性能的变化规律与变形机制。结果表明:复合坯具有良好的表面质量和冶金结合的黄铜/纯铜界面,断后伸长率达到53.1%。拉拔过程中,纯铜绞线与黄铜包覆层的协同变形程度较高。随着总变形量的增大,纯铜绞线发生塑性变形流入各纯铜线之间构成的三角弧形间隙区,当总变形量增大至50%时,三角弧形间隙区被纯铜填满。随着总变形量增加至63%,纯铜绞线内部先后产生位错胞、条状微晶带等组织;黄铜包覆层内部先后形成平面位错网、相互交叉的形变孪晶和切变带,主要变形机制依次为位错平面滑移、形变孪生和剪切变形机制。复合材料的抗拉强度由铸态的240 MPa增大到总变形量63%的519 MPa,而断后伸长率由铸态的53.1%降低到3.2%。"固/液连铸复合成形→拉拔"短流程加工方法可适用于制备高速铁路贯通地线用黄铜包覆纯铜绞线复合材料。

A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.