Toward qualification of additively manufactured metal parts: Tensile and fatigue properties of selective laser melted Inconel 718 evaluated using miniature specimens

•A “microstructure unit” that can well reflect the microstructure characteristic of SLM materials is defined.•As the ratio of specimen thickness(t) to the "microstructure unit" size(d) is reduced below one, a dramatic decrease in tensile ductility occurs.•A criterion of t/d ≥ 4 for reliable mechanical properties determined by the miniature specimens is obtained.