1999 Volume 39 Issue 1 Pages 69-74
Fatigue crack initiation and early stage of crack growth for Ti-6Al-4V and Ti-4.5Al-3V-2Fe-2Mo were investigated on notched specimens. In-situ observation of fatigue cracking processes was made using a fatigue testing machine mounted in a scanning electron microscope. It was found that Ti-4.5Al-3V-2Fe-2Mo alloy with very fine α grains of approximately 2μm exhibited a much higher fatigue strength at 107 cycles than Ti-6Al-4V alloy. However, in fatigue life an opposite trend was obtained in the short life regime. The observed fatigue behavior in both the long and short life regimes is discussed in terms of metallurgical factors responsible for the fatigue behavior of the present materials.