Dual-step solution T6 heat treatment achieves strength–ductility synergy in LPBF-fabricated AlSi10Mg alloy

Achieving an optimal balance between strength and ductility in laser powder bed fusion (LPBF) fabricated AlSi10Mg alloys through post-heat treatment remains challenging, as conventional T6 treatment often leads to a trade-off between these properties due to uncontrolled Si coarsening and insufficient precipitation. In this study, a novel dual-step solution T6 treatment (530 °C/1 h + 550 °C/1 h + 180 °C/6 h) is designed to overcome this limitation. This kinetically controlled process decouples the Si network fragmentation and solute homogenization, preventing detrimental Si coarsening. Microstructural characterization reveals that this strategy effectively refines and homogenizes the distribution of Si particles, reduces crystallographic texture anisotropy, and promotes the formation of Mg-Si co-clusters, as evidenced by scanning electron microscopy, electron backscatter diffraction, and atom probe tomography. Consequently, the dual-step T6-treated alloy exhibits a superior strength–ductility synergy, with an ultimate tensile strength of ∼340 MPa and an elongation of ∼12.3%, outperforming its single-step solution-treated counterparts. The underlying mechanisms are quantitatively elucidated through strengthening modeling, which attributes the enhancement predominantly to optimized precipitation strengthening coupled with grain refinement. This work provides a cost-effective and scalable microstructural tailoring strategy for additive manufactured Al-Si alloys.