Influence of matrix property and interfacial reaction on the mechanical performance and fracture mechanism of TiC reinforced Al matrix lamellar composites

Freeze casting is a versatile approach for the design of lamellar metal-ceramic composites with unique combination of strength and toughness. However, previous studies mainly focused on ceramic factors such as content and lamellae structure, seldom concerning the effects of metal property and interfacial structures, which, in practice, are key factors in determining the mechanical performances of the composites. In this work, we prepared three kinds of Al/TiC lamellar-interpenetrated composites with different matrix compositions (pure Al, 6061Al (Al-0.4Cu-1.0Mg-0.6Si) and ZL107 (Al-7Si-5Cu)) via freeze casting and pressure infiltration, aiming at clarifying the roles of matrix property and interfacial reaction on the mechanical properties and fracture mechanisms of the composites. The flexural strengths of pure Al/TiC, 6061Al/TiC and ZL107/TiC composites reached 355 +/- 10, 415 +/- 15 and 459 +/- 18 MPa, while the toughness values (characterized by crack-growth toughness) were 81.0 +/- 2.0, 57.6 +/- 1.2 and 43.4 +/- 1.5 MPa M-1/2, respectively. The exceptional damage tolerance of these lamellar composites was attributed to multiple toughening mechanisms such as crack deflection, uncracked-ligament bridging of ductile layers and plastic deformation of the metal matrix. However, the presence of Si in the 6061Al and ZL107 alloys weakened the stability of TiC and promoted interfacial reaction, leading to the formation of a certain number of (Al1-n Si-m)(3)Ti and Al4C3, which greatly weakened the toughness of the composites. Due to the combined effects of alloy plasticity, lamellar-interpenetrated structure and interfacial reaction, the fracture of the materials changed from a multiple cracking mode in the Al/TiC composite to a single crack propagating mode in the 6061Al/TiC and ZL107/TiC composites.