Fatigue small crack growth threshold determination of a high-Nb TiAl alloy at different temperatures by in-situ observation

摘要

The purpose of this paper is to estimate the fatigue crack growth threshold of a high-Nb TiAl alloy at the different temperatures based on scanning electron microscopy(SEM)in-situ observation.The results indicated that the fatigue crack growth threshold ΔK th of a nearly lamellar high-Nb TiAl alloy with 8% Nb content at room temperature and 750 ℃ was determined as 12.89 MPa·m 1/2 and 8.69 MPa·m 1/2,respectively.The effect of the elevated temperature on the fatigue crack growth threshold cannot be ignored.At the same time,the early stage of fatigue crack propagation exhibited multicrack initiation and bridge-link behavior.