The effect of ultrasonic impact treatment on deformation and fracture of electron beam additive manufactured Ti-6Al-4V under uniaxial tension

Microstructural Transformation and Enhanced Strength of Wire‐Feed Electron‐Beam Additive Manufactured Ti–6Al–4V Alloy Induced by High‐Pressure Torsion

“…Such a structure is typical for the Ti-6Al-4V titanium alloy obtained by additive technologies. [15][16][17][18][19][20] This structure is due to the directional heat dissipation during crystallization of the melt pool resulting in epitaxial growth of columnar primary β grains, the size of which is determined by the cooling rate of the melt pool. When the temperature of the crystallized layer is below %990 °C, the primary β-grains undergo a polymorphic β!α transformation, which develops according to the diffusion-free martensitic mechanism with the formation of a needle/plate martensitic α 0 phase.…”

“…The 3D‐printed parallelepiped‐shaped billets with the dimensions of 25 mm × 25 mm × 90 mm were successfully produced using electron‐beam melting of the Grade 5 (Ti–6Al–4V) wire of diameter 1.6 mm at the wire EBAM facility (ISPMS SB RAS, Tomsk, Russia). [ 20 ] Chemical compositions of the Grade 5 wire, assessed using a “Thermo Scientific Niton XL3t GOLDD” X‐ray fluorescence (XRF) analyzer (ThermoFisher Scientific, USA), is given in Table 1 . Wire melting was carried out in vacuum of 1.3 × 10 −3 Pa by the electron gun with plasma cathode at accelerating voltage of 30 kV.…”

“…It is worth noting that the presence of individual dislocations and extinction contours in the light-field TEM images indicates the The results presented here are in a good agreement with earlier electron microscopic studies of the Ti-6Al-4V alloy produced by wire-feed EBAM. [20] Figure 4 shows the results of electron backscatter diffraction (EBSD) analysis of the Ti-6Al-4V alloy in the initial 3D-printed state. The EBSD images in this state demonstrate a lamellar microstructure combined into large clusters with predominantly low-angle misorientation of the grain boundaries.…”

“…[19] The microstructure of the Ti-6Al-4V alloy samples produced by electron-beam wire additive manufacturing exhibits typical feature of columnar prior-β grains, within which the α/α 0 -Ti laths are observed that are collected in packages and separated by interlayers of residual β phase. [20] In addition, the 3D-printed Ti alloys manufactured by this technology are often characterized by a low volume fraction of residual β phase due to rapid solidification of the melt pool and multiple phase transformations resulting from repeated thermal cycles. [17] At the same time, the strength properties of the EBAM Ti-6Al-4V samples are often significantly lower than the strength properties of the Ti-6Al-4V samples obtained both by laser or electron-beam melting of powder feedstock and by traditional production methods (casting, stamping, etc.).…”

Transformations of the Microstructure and Phase Compositions of Titanium Alloys during Ultrasonic Impact Treatment Part II: Ti-6Al-4V Titanium Alloy

“…The authors of the article, using MD simulation, demonstrated the development of reversible  phase transformations in the Ti-6Al-4V titanium alloy during scratch testing, which made it possible to explain the experimentally observed recovery of a scratch [17][18][19]. It has been found that the migration of the twin boundaries in the titanium crystallite under tension is also governed by the development of reversible  transformations [20]. However, it remains to be seen how the significant fragmentation and disorientation of the crystal lattice in the ultrasonically treated surface layer affect the development of the strain-induced phase transformations in the Ti-6Al-4V alloy.…”