Abstract
α+β Ti-6Al-4V has been used as the structural material in various industries. Then, it is well known that two microstructures affect the fatigue strength characteristics of titanium alloy. However, it isn't known that the mechanism of the fatigue crack initiation behavior because of the smallness of crack. In this study, the fatigue crack initiations were observed using an atomic force microscope (AFM) in order to consider about fatigue properties. Additionally, replica technique was used so as microcrack to be observed. Microscopic observation of surface of test piece and fracture surface observation by SEM brought out that crack initiates primary α-phase or grain boundary of primary α-phase by slip.
