Fatigue of in situ Reinforced Ti–8.5Al–1B–1Si

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Abstract
The effect of temperature on the fatigue and fracture properties of an in situ reinforced super α alloy Ti–8.5Al–1B–1Si (wt. %) was investigated. At room temperature the as-extruded composite has a strength of 631 MPa with limited ductility. On increasing the temperature to 700 °C only a marginal drop in strength to 610 Mpa was observed along with a significant improvement in ductility to 5.9%. Low-cycle fatigue results indicate a marginal decrease in fatigue life as temperature is increased from room temperature to 700 °C. Fatigue crack growth studies in the as-extruded microstructure indicate a strong influence of R-ratio on both the threshold for fatigue crack growth and crack growth rates in the Paris regimes. At elevated temperatures, the resistance to fatigue crack growth increases with temperature below approximately 500 °C. At 600 °C, however, there is an increase in the near threshold crack growth rate due to embrittlement effects. At higher δK values , the resistance to fatigue crack growth at elevated temperatures is always better than that at room temperature. This improvement is attributed to the increase in the inherent resistance