Metal/ceramic composites from freeze-cast ceramic preforms: Domain structure and elastic properties

Innovative metal/ceramic composites produced by melt infiltration of ceramic preforms prepared by a freeze-casting technique are examined in this study. These composites exhibit a characteristic hierarchical structure: On a mesoscopic length scale, lamellar domains with sizes up to several millimetres are observed. The aim of the present study was to analyze the anisotropic elastic properties of such a composite on different length scales. Experimental studies were carried out on samples containing about 44% alumina ceramic and 56% aluminium-based alloy (Al–12Si). Ultrasonic wave velocity measurements were carried out on macroscopic poly-domain samples as well as on miniature single-domain samples. The elastic constants derived from these measurements are discussed in light of elasticity models established for lamellar and for fibrous composites.