Biphasic Synergistic Strengthening in Novel Al ₂ O ₃ /Mg Interpenetrating Phase Composites via TPMS-Based Additive Manufacturing

Balancing the strength and toughness of materials remains a long-standing core challenge in materials science. In this study, a novel design strategy for Al 2 O 3 /Mg interpenetrating phase composites (IPCs) is proposed. Al 2 O 3 ceramic scaffolds with two types of Split-P triply periodic minimal surface (TPMS) structures (shell-type and solid-type) were fabricated via stereolithography (SLA) and then infiltrated with AZ91D magnesium alloy using lost foam casting (LFC), and consequently, Al 2 O 3 /Mg IPCs were successfully fabricated. In the proposed method, cocontinuous interpenetration of ceramic and metal phases is achieved, ultimately forming a dense interlocking structure with no interfacial delamination and a relative density exceeding 95%. Quasi-static compression tests and finite element simulations confirm that the as-built composites exhibit a compressive strength of up to 187.5 MPa and a specific energy absorption of 11.18 J/g; among them, the solid-type IPC shows a slightly higher compressive strength, while the shell-type IPC demonstrates superior energy absorption performance. The excellent performance of the IPCs is attributed to the TPMS structure that effectively mitigates the local stress concentration prone to occur in traditional truss structures, along with the synergistic strengthening effect between ceramic and metal phases that substantially improves the plastic deformation capacity and energy dissipation efficiency of the composites. This study provides a new idea for the design and fabrication of high-strength and lightweight composites, which hold significant application potential in lightweight load-bearing and impact-resistant energy-absorbing fields.