FATIGUE FAILURE ANALYSIS OF ADDITIVE MANUFACTURED Ti-6Al-4V ALLOY

The additive manufactured (AM) titanium alloys show poor behavior in fatigue properties compared to the conventional wrought alloys. This behavior is influenced by the presence of typical defects originating from the of powder bed fusion process. The defects can be characterized by their type, size, morphology or by their relative position from the surface. During the AM process about three fine powder metal layers are fusing together and undergo solidification stage. In addition, the quality of the surface roughness is not good. The objective of this research is to characterize these manufacturing defects by fractographic analysis and by investigation of the metallurgical aspects and their effects on the fatigue failure. Broken specimens of AM Ti-6Al-4V alloys were macroscopic and microscopic examined using optical microscopy, scanning electron microscopy (LV-SEM) and energy dispersive X-ray spectroscopy (EDS). The specimens were characterized in the fractographic and metallographic forms. The defects were classified according to the degree of importance on the fatigue strength.