High temperature fatigue crack growth behavior of Ti-6Al-4V

Experimental evaluation of high temperature, Fatigue Crack Growth Rate (FCGR) data for Ti-6Al-4V, a titanium alloy, is presented. The FCGR data were measured at room temperature, 175, 230, 290 and 345degreesC using the Direct Current Potential Difference (DCPD) technique. Compact Tension (CT) specimens were used in the program and crack growth rates (da/dN) vs. Mode I stress intensity factor ranges (DeltaK) were plotted as a function of temperature. A temperature rise from 175 to 345degreesC did not cause a substantial increase in crack growth rates within the Stage II region where a linear relationship describes the behavior. Formation of secondary cracks, observed at higher temperatures, may have slowed the crack propagation as observed in the fractography.