Current density-dependent microstructural evolution and mechanical performance in electropulsing cyclic aging of 2195 Al-Li alloy

Abstract

This study systematically investigates the current density-dependent microstructural evolution and mechanical performance of 2195 Al-Li alloy during electropulsing cyclic aging (ECA). By employing gradient pulsed current densities (10–20 A/mm²), we elucidate the synergistic interplay between electron wind force and Joule heating in governing solute diffusion, dislocation dynamics, and precipitation kinetics. At a sub-threshold current density of 10 A/mm², negligible microstructural changes yield mechanical properties identical to those of the as-received (AR) alloy. At 15 A/mm², electron wind force-driven dislocation reorganization dominates over precipitation, inducing Portevin-Le Chatelier (PLC) effects due to enhanced solute mobility. Remarkably, at 20 A/mm², the alloy achieves peak-aged strength (UTS: 548 MPa; YS: 516 MPa) within 5 hours–75 % faster than conventional T8 aging (155 °C/20h)-through accelerated T₁ phase (Al₂CuLi) nucleation and vacancy-mediated solute diffusion. Thermal-athermal synergy reduces nucleation barriers and enables dislocation density reduction, while coherent T₁ phases precipitates counteract strength loss. Fractography reveals current density-dependent failure modes: ductile transgranular fracture (ECA15) transitions to brittle intergranular fracture (ECA20) due to S’ phase (Al₂CuMg) formation at grain boundaries. These findings establish a paradigm for optimizing strength-ductility trade-offs via current density modulation, demonstrating 300 % aging efficiency gains, with broad implications for energy-efficient aerospace alloy processing.