Microstructure and Mechanical Behavior of Ultrafine-Grained Titanium

Abstract

Ultrafine-grained titanium was processed by severe plastic deformation (SPD). The SPD was carried out by equal channel angular pressing (ECAP) at high temperature. The ECAPprocessed sample was further deformed by conventional techniques such as radial forging and drawing. The microstructure was characterized quantitatively by X-ray diffraction line profile analysis and transmission electron microscopy after each step of deformation. The effect of procesing routes on the mechanical behavior was also studied. It was found that the conventional deformation processes after ECAP result in further increment in dislocation density and strength at the expense of ductility.

Chemical etching of titanium samples

“…Grade 2 is produced by the traction of raw titanium into a bar, whereas nano titanium is produced by a treatment named equal-channel angular pressing [2]. During the pressing a very high mechanical stress arises.…”

Formation and Thermal Stability of the ω-Phase in Ti–Nb and Ti–Mo Alloys Subjected to HPT

“…However, these alloys are seldom used due to the fact of their lower strength in comparison with widely applied biocompatible Ti alloys, such as Ti-6Al-7Nb, Ti-5Al-2.5Fe, or Ti-6Al-4V, which possess restricted biocompatibility and relatively high Young's modulus [1,9]. Using the methods of severe plastic deformation (SPD), it is possible to improve the strength of materials due to the refinement of the microstructure [10,11] and to reduce the Young's modulus due to the phase transformations caused by SPD [4]. For example, the high-temperature deformation of Grade-2 purity titanium by the equal-channel angular pressing (ECAP) increases its yield strength from 330 to 652 MPa due to the decrease in grain size to a few dozens of nanometers together with an increase in dislocation density [11].…”

“…Using the methods of severe plastic deformation (SPD), it is possible to improve the strength of materials due to the refinement of the microstructure [10,11] and to reduce the Young's modulus due to the phase transformations caused by SPD [4]. For example, the high-temperature deformation of Grade-2 purity titanium by the equal-channel angular pressing (ECAP) increases its yield strength from 330 to 652 MPa due to the decrease in grain size to a few dozens of nanometers together with an increase in dislocation density [11]. The high-pressure torsion MPa due to the decrease in grain size to a few dozens of nanometers together with an increase in dislocation density [11].…”

“…For example, the high-temperature deformation of Grade-2 purity titanium by the equal-channel angular pressing (ECAP) increases its yield strength from 330 to 652 MPa due to the decrease in grain size to a few dozens of nanometers together with an increase in dislocation density [11]. The high-pressure torsion MPa due to the decrease in grain size to a few dozens of nanometers together with an increase in dislocation density [11]. The high-pressure torsion (HPT) of commercially pure titanium (Grade 4) increases the ultimate tensile strength up to 1600 MPa due to the decrease in grain size [12].…”

Anisotropy of uni-axial and bi-axial deformation behavior of pure Titanium after hydrostatic extrusion

“…Nowadays, development of severe plastic deformation (SPD) techniques [3] has enabled formation of ultrafinegrained (UFG) microstructure in CP Ti leading to its enhanced mechanical strength. These SPD methods include equal-channel angular pressing (ECAP) [4,5], ECAP in combination with extrusion (or rolling, swaging, drawing) [6][7][8], high pressure torsion (HPT) [9,10], cryo-rolling followed by annealing [11], cross rolling [12,13], etc. Hydrostatic extrusion appears as one of the most promising SPD methods for fabrication of UFG CP Ti since it has some advantages [14].…”