An investigation of the effects of temperature on fatigue crack growth in a cast lamellar Ti–45Al–2Mn–2Nb+0.8 vol.% TiB2 alloy1

This paper presents the results of a study of the effects of temperature on fatigue crack growth in Ti–45Al–2Mn–2Nb+0.8 vol.% TiB2 gamma titanium aluminide intermetallics. Fatigue crack growth rate data are presented for cast lamellar microstructures at 25, 450 and 700 °C. Slower fatigue crack growth rates at 700 °C (compared to those at 450 °C) are also explained by the crack-tip shielding provided by oxide-induced wedging, which is analyzed using a modified Dugdale–Barenblatt model. The observed cyclic cleavage modes are found to be similar at 25, 450 and 700 °C, and the implications of the results are discussed for potential applications of cast XD™ gamma alloys in the intermediate-temperature regime between 450 and 700 °C. ™XD is a trademark of the Lockheed Martin Corporation of Marietta, GA.