Strengthening of a Ti–6Al–4V titanium alloy by means of hydrostatic extrusion and other methods

The mechanical properties of Ti–6Al–4V titanium alloy with four different microstructures were studied: a submicrocrystalline structure of grain size about 0.4 μm, produced by multiaxial forging in stages at temperatures decreasing from 700 to 550 °C; a cold-worked submicrocrystalline structure produced by cold rolling after multiaxial forging; a mixed lamellar and submicrocrystalline globular structure produced by hydrostatic extrusion at 600 °C and a microcrystalline structure produced by conventional heat treatment after multiaxial forging at 930 °C. The highest strength, about 1500 MPa, was found for both the cold-worked submicrocrystalline and the hydrostatically extruded materials, but the extruded material had a higher ductility, i.e., higher total elongation and elongation before necking. The submicrocrystalline and the microcrystalline materials exhibited moderate strength of 1300 and 1050 MPa, respectively, with an elongation to failure of about 9%. The results were interpreted in terms of the microstructural features and the strengthening mechanisms resulting from the production processes.