Axial fatigue testing of Ti–6Al–4V using an alternative specimen geometry fabricated by metal injection moulding

The hourglass-shaped specimen, which is commonly used for axial fatigue testing, cannot be easily fabricated by metal injection moulding. Consequently, this work aimed at evaluating the performance of an alternative specimen (dog bone geometry) for fatigue characterisation. Additionally, an effort towards the assessment of the fatigue damage with specimens fatigued until halflife was made. The alloy used in this study, serving as an example for the test validation, was Ti–6Al–4V. The feasibility of using the specimens for fatigue testing was confirmed with a narrow scatterband, however, only in the range of 10⁵ cycles. The crack initiation sites were always found on the surface associated with quasi cleavage facets. Specimens fatigued until halflife showed a decrease in ductility in conventional tensile testing; nonetheless, the ultimate tensile strength remained unchanged.