Small Specimen Test Technology for Evaluation of Fatigue Properties of Fusion Structural Materials

Abstract

Fatigue tests of ferritic/martensitic steels for fusion reactor application were carried out at room temperature using mini-sized and full-sized hourglass type fatigue specimens, as the basic study of small specimen testing techniques, which are indispensable for the effective use of the limited volumes of material testing reactor and proposed intense neutron sources. The FIB micro-sampling technique was applied to make the cross sectional thin foil specimen from the fatigue crack tip nearby the fractured surface. Effects of specimen size on fatigue properties, such as lifetime, plastic strain range and stress range, were not significant in the specimens used. TEM examination around the crack tip revealed original martensitic lath structure had changed to polygonization-like-structure and fatigue crack had been initiated along pre-austenite grain boundary.