Effect of Ultrasonic Impact Treatment on Microstructure and Fatigue Life of 3D Printed Ti-6Al-4V Titanium Alloy

Ultrasonic impact treatment (UIT) of Ti-6Al-4V alloy specimens, produced by wire-feed electron beam additive manufacturing technology, was carried out using a Co-WC hard alloy striker. Using the methods of X-ray diffraction analysis and transmission electron microscopy, it has been shown that UIT leads to the appearance of compressive macrostresses in the surface layers of the specimen, elastic microdeformations in the crystal lattice of the alpha-phase, formation of a gradient structure from nanocrystalline structure at a depth of up to 5 mu m to submicrocrystalline structure of the alpha-phase at a depth of 15 to 40 mu m. A nanocrystalline phase of titanium oxides is formed in the grains of the alpha-phase. The UIT results in an increase in microhardness and fatigue life. Fractographic analysis of specimen fractures after cyclic stretching in low-cycle fatigue mode has been carried out.