Orientation Dependence of Fatigue Fracture Behavior in Pure Titanium Single Crystals
Masayuki TSUSHIDA, Takahiro SAKAMOTO, Hiromoto KITAHARA and Shinji ANDO
Abstract:To investigate fatigue fracture behavior of small titanium single crystals, plain bending fatigue test method for thin sheet specimens was developed. One end of the sheet specimen was fixed at a voice coil of a loudspeaker and the other end was set free. A bending mode resonance occurs in the specimen due to forced vibration at the fixed end. In A-specimen whose surface plane and loading direction were (0001) and [11_20], the fatigue crack propagated parallel to {1_100} plane and striation-like markings were observed on the fatigue fracture surfaces. In B-specimen with (0001) surface and [1_100] loading direction, the fatigue crack also propagated parallel to {1_100} plane as similar to A-specimen. These fatigue cracks are deduced to extend by alternating shear on two intersecting prismatic slip systems at the crack tip. In D-specimen with (1_100) surface and [11_20] loading direction, the fatigue crack propagated along [0001] with prismatic slip. In E- and F-specimen with [0001] loading direction, these fatigue cracks propagated parallel to (0001) with {10_12} twinning. As a result, S-N plots of each specimen showed strong orientation dependence. Key Words:Titanium, Fatigue fracture, Fatigue crack, Single crystal, S-N plots, Fracture surface