From crack-prone to crack-free: Eliminating cracks in additively manufacturing of high-strength Mg2Si-modified Al-Mg-Si alloys.

• L-PBFed Al- x Mg 2 Si alloy achieve the transition from crack-prone to crack-free. • Crack elimination is highly associated with eutectic filling and grain refinement. • The YS and EL of L-PBFed Al-9Mg 2 Si alloy are 397 MPa and 7.3 %, respectively. • Strengthening is mainly caused by the interaction between Mg 2 Si and the dislocation. Large solidification ranges and coarse columnar grains in the additively manufacturing of Al-Mg-Si alloys are normally involved in hot cracks during solidification. In this work, we develop novel crack-free Al-Mg 2 Si alloys fabricated by laser powder-bed fusion (L-PBF). The results indicate that the eutectic Mg 2 Si phase possesses a strong ability to reduce crack susceptibility. It can enhance the grain growth restriction factor in the initial stage of solidification and promote eutectic filling in the terminal stage of solidification. The crack-free L-PBFed Al- x Mg 2 Si alloys (x = 6 wt.%, 9 wt.%, and 12 wt.%) exhibit the combination of low crack susceptibility index (CSI), superior ability for liquid filling, and grain refinement. Particularly, the L-PBFed Al-9Mg 2 Si alloy shows improved mechanical properties (e.g. yield strength of 397 MPa and elongation of 7.3 %). However, the cracks are more likely to occur in the region near the columnar grain boundaries of the L-PBFed Al-3Mg 2 Si alloy with a large solidification range and low eutectic content for liquid filling. Correspondingly, the L-PBFed Al-3Mg 2 Si alloy shows poor bearing capacity of mechanical properties. The precise tuning of Mg 2 Si eutectic content can offer an innovative strategy for eliminating cracks in additively manufactured Al-Mg-Si alloy. [Display omitted] [ABSTRACT FROM AUTHOR]