Controllable phase transformation and static recrystallization inducing excellent strength-plasticity synergy in powder sintered Cu-18Sn-0.3Ti alloy

Abstract

Coarse grains and uncontrolled phase constituents have significant adverse effects on the mechanical properties of Cu-18Sn-0.3Ti alloy, thus restricting the preparation of Nb₃Sn superconducting wires with higher critical current density. In this work, the strength-plasticity enhancement of powder sintered Cu-18Sn-0.3Ti alloy was realized through inducing static recrystallization and controlling phase transformation. The ultimate tensile strength, yield strength and elongation of the alloy were increased from 507.2 MPa, 229.4 MPa and 23.4% to 677.0 MPa, 359.9 MPa and 38.9%, respectively. Through first-principles calculations, molecular dynamics simulation, detailed thermodynamic assessment and kinetic analysis, δ-Cu₄₁Sn₁₁ and ε-Cu₃Sn phases were determined to be harmful to the plastic deformation of alloy, and the annealing temperature of no more than 600°C can reduce the volume fraction of Sn-rich phases, promote the phase transformation from δ phase to β-Cu₁₇Sn₃ and γ-Cu₃Sn phases, and inhibit the formation of ԑ phase, which verified the experimental results. The phase constituent conductive to plastic deformation of alloy, fine grains and high-density annealing twins were the main reasons for the strength-plasticity enhancement of alloy. The results lay a foundation for the preparation of Nb₃Sn superconducting wires and provide theoretical guidance for the strength-plasticity enhancement of other multi-component alloys.