Synchronized Enhancement of Electrical Conductivity and Mechanical Properties of A356 Alloy via Gd Alloying

Conventional A356 (Al-Si-Mg) alloy commonly exhibits an inherent trade-off between electrical conductivity (EC) and mechanical properties, limiting its further applications as conductive structural components. To address this issue, different contents of Gd (0.1, 0.3, and 0.5 wt pct) were added to A356 and followed by solution and aging treatment. The results demonstrate that the addition of Gd refined and optimized the α-Al grains and the secondary dendrite arm spacing (SDAS) of eutectic Si, while promoting the formation of GdAl₂Si₂ phase, which reduced the solid solubility of Si in the matrix. After heat treatment, the eutectic Si was further refined and spheroidized, while Mg₂Si phase emerged. It was found that the addition of 0.3 wt pct Gd significantly enhanced the EC of A356 from 37.41 to 41.17 pctIACS. Furthermore, the T6-treated A356-0.3Gd sample achieved significant enhancements in both EC and mechanical properties. Specifically, compared with the T6-treated A356, the EC, ultimate tensile strength (UTS), yield strength (YS), and elongation (El) of T6-treated A356-0.3Gd sample increased from 39.99 pctIACS, 297, 256 MPa, and 2.3 pct to 42.90 pctIACS (increased by 7.28 pct), 315 MPa (increased by 6.06 pct), 273 MPa (increased by 6.65 pct), and 3.8 pct (increased by 65.21 pct). This study proposed a novel approach for improving both EC and mechanical properties of Al-Si-Mg alloys through Gd-alloying combined with subsequent heat treatment.