Enhanced strength-conductivity trade-off in Al-Mg-Si alloys with optimized Mg/Si ratio

This study evaluated the potential for an enhanced strength–conductivity trade-off in Al-Mg-Si alloys with optimized Mg/Si ratios. In cases of the consistent total amounts of Mg and Si atoms, evident differences in hardness and conductivity manifested during artificial aging, contingent on the Mg/Si ratio investigated. The alloy with an Mg/Si ratio of 1.18 displayed a superior trade-off between strength and conductivity, yielding a yield strength of 305 MPa coupled with a remarkable conductivity of 51.57%IACS and 199.7 W/m/K. Alloys characterized by low Mg/Si ratios exhibited a significantly higher precipitates fraction than those with high Mg/Si ratios because of the accelerated age-precipitation kinetics. This resulted in the improved strength owing to the enhanced precipitation strengthening contribution. A constitutive model considering both fraction and structural composition of the precipitates was established to elucidate the mechanism of varying Mg/Si ratio on conductivity. Variations in the residual Mg and Si within the matrix have been demonstrated to predominantly account for the disparities in conductivity across alloys with distinct Mg/Si ratios. The substantial precipitation in the alloy with an Mg/Si ratio of 1.18 induced heightened depletion of both Mg and Si, consequently achieving a comparatively elevated conductivity concomitant with its relatively superior strength.