THE EFFECT OF ELEVATED TEMPERATURE AND ENVIRONMENT ON THE FATIGUE CRACK GROWTH CHARACTERISTICS OF Ti?6Al?2Sn?4Zr?2Mo?0�1Si

Abstract Renewed interest in utilizing titanium at elevated temperature has led to the development of creep resistant near α-alloys. Present work is concerned with the fatigue crack growth characteristics of one such alloy, Ti–6Al–2Sn–4Zr–2Mo–0·1Si, as a function of temperature, environment, and processing history. Increasing crack growth rates were observed in the order, vacuum (298K), vacuum (811K), air (298K), and air (811K). An empirical expression based upon crack opening displacement considerations was found to fit the crack growth data in all but the air (811K) test. The pronounced increase in growth rates in air at 811K, particularly at low ΔK, was caused by oxidation, whereas the increase in growth rates at 811K in vacuum was the result of a decrease in modulus. Processing variables and test frequency had little effect on crack growth rates.