EFFECT OF PHASE ARCHITECTURE ON THE THERMAL EXPANSION BEHAVIOR OF INTERPENETRATING METAL/CERAMIC COMPOSITES

摘要

Interpenetrating metal/ceramic composites (IPC) consisting of percolating metallic and ceramic phases offer a good combination of properties. Thermal expansion behavior of two IPCs with different phase architectures is studied in this work during thermal cycling between RT and 500 ℃. The composites were fabricated by melt infiltration in open porous ceramic preforms. One of the preform types was made by freeze-casting and had a lamellar structure; while the other type was fabricated by burning out cellulose place holders and had a highly open porous structure. Results show that the phase architecture strongly influences the thermal expansion of the composites. Freeze-east samples display pronounced anisotropy - the thermal expansion coefficient (CTE) being low parallel to the freezing direction and high transverse to this direction. Only slight anisotropy is displayed by the highly open porous alumina based composite, with marginally higher CTE along the preform press direction. Thermal strains and CTEs of the highly open porous alumina based composite lie within the extremal values of the composite based on the freeze-east preform. Thermal expansions of the composites correlate well with preform stiffness, with highest thermal expansion being observed along the most compliant directions in both composites.