Simultaneous improvement of strength and conductivity in 6101 alloy via pre-aging and variable-temperature rolling

Solid-solution 6101 alloy was treated by pre-aging and variable-temperature rolling (VTR) in the present study. Electrical conductivity and tensile strength were tested at the final aging state. The relationship and mechanism among "defect-recovery and recrystallization/precipitation-electrical conductivity/strength" were deeply elucidated through OM and TEM characterization. The results show that the effect of pre-aging time on the initial improvement speed( v i ) and maximum electrical conductivity ( σ max ) of VTR alloy is opposite; a pre-aging time of 30 min to 1 h can maintain a high σ max without significant loss of v i . The pre-aging combined with the VTR process can greatly improve the mechanical strength of 6101 alloy: the alloy pre-aged at 230 °C for 1h achieves a yield strength of up to 261 MPa at the stage 2 of final aging and 194 MPa at the stage 4, with a corresponding σ max of 60.6% IACS, showing excellent comprehensive performance. During the VTR process, dynamic recovery and dynamic precipitation occur in the alloy, forming a stable high-density dislocation cell structure, which is effectively pinned by precipitates during subsequent aging, thereby suppressing recrystallization and dislocation annihilation and significantly increasing the yield strength to 261 MPa. During final aging, fine Mg 2 Si phases dissolve back, coarse phases grow into short rods, the solute concentration and defects in the matrix decrease, and electron scattering is weakened, resulting in an electrical conductivity of 60.6% IACS and realizing the synergistic improvement of strength and electrical conductivity.