Effect of freeze speed on the microstructure and damage-tolerance behavior of bio-inspired ZL205A/silicon carbide composites

In the present research, we produced porous silicon carbide (SiC) scaffolds with lamellar and uniformly distributed structures by unidirectional and quick freeze casting, respectively. Subsequently, we prepared the ZL205A/SiC composites with lamellar and uniformly distributed structures by infiltrating a molten ZL205A alloy into the porous SiC scaffolds. The influence of freezing speed on the damage-tolerance behavior and the toughening mechanism of the resultant composites were investigated. We found that because of multiple toughening mechanisms, the layered composites exhibited much higher strength and toughness as compared with the uniformly distributed composites. The lamellar composites manifested superior specific modulus and a unique combination of specific strength and toughness, which was comparable to those of titanium and magnesium alloys. We also observed that the thicknesses of alloy layers and SiC lamellae of the composites reduced with decreasing cooling temperature in freeze casting. Furthermore, the refinement of lamellae size at higher freezing speeds caused a decrease in the damage-tolerance ability of the composites because of weak toughening effect