Abstract
Uniaxial tension fatigue tests were carried out in air and high vacuum environments using pieces made of Ti-6Al-4V alloy with several surface finishings. Effects of high vacuum environment on high cycle fatigue were investigated based on results of fatigue tests and the data arranged by initial stress intensity factor range (ΔK_<ini>). Considering results of fatigue tests that interior-originating fractures occurred near yield stress in high vacuum environment, it is necessary to pay attention to the interior-originating fracture in case of using this material in vacuum environment like space. Fatigue lives in high vacuum strongly depended on cyclic stress compared with those in air as stress decreased. As for data arranged by ΔK_<ini>, the dependence of the threshold stress intensity factor range (ΔK_<th>) on crack size in high vacuum is expected to be stronger than that in air.
