FATIGUE GROWTH BEHAVIOR OF SHORT CRACKS IN #alpha#-#beta#-SiAlON AT 1200 deg C

摘要

Experimental results are presented on subcriticalcrack growth under sustained and cyclic loads in gas pressuresintered (GPS) #alpha#-#beta#-Sialon at 1200 deg C. Staticand cyclic fatigue crack growth rates are obtained by"controlled" surface cracking from Vickers indentations in barsloaded in 4-point bending. At the lower stress intensity factors,cyclic fatigue crack growth rate is slower than that of staticfatigue at the same stress intensity factor. At higher stressintensity factors, the crack growth rates both static and cyclicfatigue are almost the same. Electron microscopy analysis inthe crack-tip damage zone indicates that the fatigue stresseshelp aid the crystallization process of the amorphous phase andlead to increase the role of dislocation plasticity during hightemperature fatigue fracture.