Simulated flight fatigue of an alpha/beta titanium alloy

Simulated flight (FALSTAFF) fatigue tests have been carried out on precracked single edgenotch test-pieces of (Ti4Al4Mo2Sn0.5Si) IMI 550 titanium alloy. Predictions of simulated flight fatigue behaviour have been made from constant amplitude fatigue data, using a damage accumulation approach, with no allowance for load history. The predicted lives were conservative compared with the measured lives, and accurate within a factor of approximately two. Retardation of fatigue crack growth increased with increasing load amplitude. The microstructure produced by β-solution heat treatment at 1010°C, followed by ageing, was found to improve simulated flight fatigue lives by up to approximately 100% compared with standard solution treatment at 900°C, followed by ageing.