Fine grains, dispersed phases and strong crystal defect interactions inducing excellent strength-ductility synergy in powder sintered Cu–18Sn-0.3Ti alloy via hot extrusion and solution treatment

Abstract

In order to prepare the Cu–18Sn-0.3Ti alloy with excellent mechanical properties to realize the favorable collaborative deformation of Cu–18Sn-0.3Ti alloy and Nb in the preparation process of Nb3Sn superconducting wires by bronze method, the hot extrusion process of the Cu–18Sn-0.3Ti alloy prepared by Direct Current assisted Hot Pressed sintering based on micron atomized spherical alloy powders was systematically investigated by the combination of experiments and finite element simulation in this work. The ultimate tensile strength, yield strength and elongation can reach 683.5 MPa, 414.3 MPa and 33.3 %, respectively, through the optimization of hot extrusion parameters and subsequent solution treatment. The results show that hot extrusion with high strain rate induced the formation of fine α grains and dispersed δ phases. Especially, strong dislocations-annealing twins (ATs) interaction occurred, which was manifested as the pile-up of dislocations at twin boundaries of ATs, slippage of dislocations in multiple directions inside ATs and storage of dislocations inside ATs. Meanwhile, the high strain rate induced the formation of deformation twins inside partial grains. The grain refinement of α matrix, formation of dispersed δ phases and strong interactions of crystal defects were the main reasons for the strength-ductility enhancement of hot extruded samples, and laid an excellent microstructure foundation for further improving the mechanical properties of alloy by subsequent solution treatment. The results not only describe a feasible method for simultaneously enhancing the strength and ductility of Cu–18Sn-0.3Ti alloy, but also provide a theoretical guidance for the strength-ductility enhancement of multicomponent alloys.