Quantifying strengthening mechanisms and strength-elongation relationship in annealed pure Al wires

Abstract

Pure Al wires used for overhead transmission lines undergo continuous microstructural and mechanical property evolution due to long-term thermal service, yet the quantitative relationship between these changes remains unclear. In this study, isothermal annealing treatments (90-250°C) were performed to simulate the thermal service conditions of pure Al wire, followed by comprehensive mechanical and microstructural characterization. The results demonstrate that as the annealing temperature increases to 250°C, the yield strength and the ultimate tensile strength of the as-received pure Al wires significantly decrease from 200.4 MPa and 207.4 MPa to 72.5 MPa and 97.6 MPa, respectively, while uniform elongation increases from 2.0% to 12.6%, demonstrating a typical strength-elongation trade-off. Quantitative analysis of the strengthening mechanisms reveals that grain boundary strengthening remains dominant in both as-received and annealed pure Al wires, while dislocation and texture strengthening decrease significantly after annealing at 90°C and disappear entirely at 250°C. Moreover, a quantitative model for the strength-elongation relationship was developed based on work hardening models, demonstrating good agreement with experimental data and providing new insights for predicting the performance of pure Al wires under thermal service conditions.