Micromechanisms of Creep-Fatigue Crack growth in α'-β'-SiAlON at 1200 deg. C

摘要

The cyclic fatigue crack growth characteristics of gas pressure sintered (GPS) Y-α'-β'-Sialon at 1200 deg. C were examined by 'controlled' surface cracking from Vickers indentations in bars loaded in four- point bending. The stress intensity factor for semi- elliptical surface cracks in bending was calculated in terms of the stress and dimensions of the subcriti- cally growing cracks. For comparison, static fatigue crack growth experiments were also carried out on the material. Similar to the fatigue crack growth behaviour of Si_3N_4 at ambient temperature, the high- temperature static and cyclic fatigue crack growth rates showed three characteristic regions having a plateau with a lowest Paris exponent.