High-temperature deformation behavior of SiC-AlN ceramic alloys with fine-grained microstructure

It was recently found that SiC-AlN solid solutions can be formed over a wide compositional range and better mechanical properties were obtained particularly at room temperature for the SiC-AlN alloys than the end number materials. The present study was intended to investigate the high-temperature strength and deformation behavior of the SiC-AlN solid solution. For this purpose, superfine grained SiC-AlN solid solution and its composite samples were prepared by a reaction HIP-sintering process, and their fracture strength and deformation behavior were evaluated up to 1773K by using a newly-developed Small Punch (SP) testing method. It has been found that high fracture strength is obtained up to 1473K, and below this temperature the load-deflection curve is linear, indicating typically brittle behavior. At 1773K, plastic-like deformation behavior was observed and it intensified with decreasing strain rate. The fractographic observation suggested that the grain boundary sliding enhanced by the ultrafine grained-microstructure was predominately responsible for the appearance of the non-linear deformation at high temperature.