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7xxx Al alloys such as Al-Zn-Mg-Cu are typical lightweight materials of excellent mechanical performance. Their near-net-shape manufacturing by selective laser melting (SLM) additive manufacturing, however, remains challenging due to hot-cracking prone nature of these alloys, when subjected to rapid solidification during the SLM process. In this study, we propose that co-incorporation of submicron Si and TiB₂ to an Al-Zn-Mg-Cu alloy is capable to solve the long-standing problem by reducing solidification shrinkage and, simultaneously, enhancing its fracture toughness. Results show that solidification cracks indeed have been eliminated by the co-incorporation, along with much-refined microstructure. The resultant mechanical properties are high in ultimate tensile (556 ± 12 MPa) and yield strengths (455 ± 4.3 MPa). For disclosing the underlying mechanism, analytical means including high-resolution computer …