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Abstract 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. Graphical Abstract Unlabelled Image Highlights • The ZL205A/SiC composites with lamellar and uniformly distributed structures were prepared. • The microstructure of the composite was adjusted by manipulating the freezing rate of the SiC slurry. • Lamellar composites exhibited much higher strength and toughness as compared with the uniformly distributed composites. • The refinement of lamellae size caused a decrease in damage-tolerance ability of the composites. [ABSTRACT FROM AUTHOR]

Silicate-bonded porous SiC scaffolds with lamellar structures were prepared by freeze casting and liquid-phase sintering. It was found that the viscosity and solidification velocity of SiC water-based slurries with 30 vol% solid loading decreased with increasing Al 2 O 3 –MgO (AM) addition. As the AM content increased from 10 to 30 wt%, the lamellae of the sintered scaffolds became denser and the porosity decreased from 69±0.5% to 62±0.5%, while the compressive strength improved from 25±2 to 51±2 MPa. The dynamics of pressureless infiltration for an Al–12 Si–10 Mg alloy on the SiC porous scaffold was measured and the composites with lamellar-interpenetrated structures were successfully produced. Both the compressive strength and the elastic modulus of the composites increased with increasing AM content. The maximum strength reached 952±24 MPa and the highest elastic modulus about 156 GPa, respectively, in a longitudinal direction, increasing about 32% and 11% as compared with those of the composites without AM. [ABSTRACT FROM AUTHOR]

Porous laminated SiC scaffolds with initial solid loadings of 20–40 vol% were prepared by freeze casting and then sintered at 1200 °C for 2 h in air to produce a SiO 2 layer. Subsequently, the preforms were pressureless-infiltrated by an Al–12 wt% Si–10 wt% Mg alloy in a N 2 atmosphere, forming a lamellar-interpenetrated structure in the composites. The resultant composites were investigated by compression tests and ultrasonic pulse echo measurements in the longitudinal and transverse directions, exhibiting weak orthotropic properties. The highest compressive strength (722±35 MPa) was achieved in the samples with 30 vol% SiC in a longitudinal direction and the largest elastic modulus (163 GPa) was exhibited in the 40 vol% SiC composites. [ABSTRACT FROM AUTHOR]

Lightweight and high-strength AZ91/SiC composites with lamellar structures were successfully prepared by using freeze casting (ice-templating) and reactive infiltration techniques. The infiltration dynamics was measured and activation energy calculated to be 7.74 kJ/mol. The compressive and flexural strengths of the composites with 30 vol% initial solid load reached 743±20 MPa and 599±44 MPa, about 1.8 and 1.5 times of those of the AZ91 alloy, respectively. [ABSTRACT FROM AUTHOR]