On the work-hardening behaviour of the additively manufactured Al-Si-Mg alloys: Composite-like versus networked microstructure

Al-Si-Mg alloys are widely used for manufacturing components via laser powder bed fusion in various industrial applications where ductility and the capacity to accommodate the strain hardening are key criteria. The ductility of the laser powder bed-fused Al alloys has become a crucial property due to their fine cellular microstructure. Post-processing heat treatments improve ductility, but resultant microstructural changes affect the work-hardening behaviour, deformability, and uniform elongation values. This study aims to investigate the work-hardening capability, uniform elongation and deformability of AlSi7Mg and AlSi10Mg samples after different post-processing heat treatments by using tensile tests, optical and scanning electron microscopies. At aging temperatures below 200°C, the fully cellular structure of eutectic Si governs both the work-hardening behaviour and the strengthening mechanisms, despite the precipitation phenomenon. When direct-aging temperatures exceed 200°C, the coarsening of the Si-eutectic network modifies work-hardening behavior (Stages 1-3), accentuating the effects induced by the precipitates. Artificial aging highlights the role of precipitates in controlling both work-hardening properties and deformability.