Abnormal mechanical hysteresis behavior of Tyranno-ZMI SiC/SiC containing Ti₃Si(Al)C₂

This work studied the effect of tough phase Ti₃Si(Al)C₂ on the mechanical hysteresis behavior of SiC/SiC. Different from continuous fibers reinforced brittle ceramic matrix composites, the mechanical hysteresis behavior of SiC/SiC containing Ti₃Si(Al)C₂ shows some abnormal phenomena: as peak applied stress increases during cyclic loading-unloading-reloading tests, the thermal residual stress values exhibit highly dispersion and the thermal misfit relief strain shows abnormally slow growth. These abnormal phenomena are caused by the reduction of transvers cracks (perpendicular to loading fibers) and the generation of hoop cracks (parallel to loading fibers). The plastic deformations of Ti₃Si(Al)C₂ prevents the transverse cracking of modified matrix, while promoting the hoop cracking of SiC matrix prepared by chemical vapor infiltration (CVI-SiC). Hoop cracking occurs within the transition zone containing amorphous SiO₂ layer and carbon layer in CVI-SiC matrix. The combination of weak transition zone and strong modified matrix finally leads to the occurrence of hoop cracking.