Microstructure and mechanical and thermal properties of ternary carbides in Hf–Al–C system

• Published in: Acta materialia 2009-05, Vol.57 (9), p.2765-2774
• Main Authors: He, L.F., Bao, Y.W., Wang, J.Y., Li, M.S., Zhou, Y.C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Carbides; Exact sciences and technology; High temperature; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical property; Metals. Metallurgy; TEM; Thermal property
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2009.02.027

A Hf–Al–C composite composed of Hf 3Al 3C 5, Hf 2Al 4C 5 and Hf 3Al 4C 6 has been successfully synthesized by a hot pressing method; its microstructure and mechanical and thermal properties were systematically characterized. Hf–Al–C composite conserves the high hardness and stiffness similar to HfC. Interestingly, the composite exhibits much higher strength and fracture toughness than HfC due to its fine and anisotropic grains. Diffusion-accommodated grain-boundary sliding of Hf–Al–C ceramics at high temperature is inhibited by glass-free grain boundaries and tight interlocking of grains at grain-edge triple junctions, resulting in high remaining stiffness up to 1600 °C. Dislocations on the basal planes of Hf–Al–C ceramics with a Burgers vector of 1 3 〈 1 1 2 ¯ 0 〉 can be activated at high temperature. Hf–Al–C composite shows higher coefficient of thermal expansion and specific heat capacity as well as lower thermal conductivity than HfC. The superior mechanical and thermal properties make Hf–Al–C compounds good high-temperature structural materials.