Influence of Ceramic Freeze-Casting Temperature on the Anisotropic Thermal Expansion Behavior of Corresponding Interpenetrating Metal/Ceramic Composites

Interpenetrating phase metal/ceramic composites (IPC) offer an optimum combination of strength, stiffness, wear resistance, and thermal properties. Ceramic preforms fabricated by freeze-casting are optimum for IPC fabrication due to the lamellar open porous structure of the preforms and their excellent permeability for melt infiltration. While the thermal properties of IPCs based on freeze-cast ceramic preforms have been sporadically studied, to the best of our knowledge, this is the maiden work where the influence of ceramic preform’s freeze-casting temperature and preform anisotropy on the thermal expansion behavior of the resulting IPC has been systematically investigated. Preforms were freeze-cast at two different temperatures, − 10, and − 30 °C. Thermal expansion behavior was studied by thermal cycling at a slow rate between room temperature and 500 °C. Both thermal strain and coefficient of thermal expansion (CTE) were determined as a function of temperature along the freezing direction and along a direction orthogonal to it. Elastic anisotropy present in the composite samples was estimated prior to the thermal expansion measurements using a non-destructive ultrasonic technique. The results showed that the lamellar anisotropic preform structure and corresponding elastic anisotropy had a strong influence on the composite’s thermal expansion behavior—generally, the highest thermal strain and CTE were achieved along the most compliant direction. The measured CTE values were compared with relevant analytical models.