Crack propagation path deflection induced by α-Mg / LPSO interface and its effect on the fracture toughness of cast Mg-RE-Zn alloys

The poor fracture toughness limits the widespread application of high-strength cast Mg-Re-Zn alloys. Regulating the alloy microstructure, with phases such as α-Mg, blocky LPSO (long-period stacking order), and lamellar LPSO, offers various possibilities to enhance ductility by casting and heat treatment. This study categorizes different interface types concerning crack initiation, propagation, and ultimate fracture toughness. It distinctly presents the results of interface modulation related to alloy composition and heat treatment, elucidating the influence on crack initiation and propagation paths. Consequently, it proposes structural configurations rule and relevant heat treatment processes that can optimize and improve alloy fracture toughness. Blocky LPSO should have appropriate dispersion and size while avoiding lamellar LPSO.