High-Pressure Torsion of Ti: Synchrotron characterization of phase volume fraction and domain sizes

Raúl E Bolmaro,Maurizio Ferrante,Vitor L Sordi,Megumi Kawasaki,Terence G Langdon,Heinz-Günter Brokmeier

doi:10.1088/1757-899x/63/1/012147

Abstract

Rods of grade 2 Ti were processed by Equal-Channel Angular Pressing (ECAP) (ϕ = 120° at 573 K) employing 2, 4 and 6 passes. The same billets were further deformed by High- Pressure Torsion (HPT) at room temperature, varying both the hydrostatic pressure (1 and 6 GPa) and the number of rotations (n = 1 and 5). The ECAP and HPT samples were studied by synchrotron radiation at DESY-Petra III GEMS line. On the ECAP samples, textures were thus determined while for both ECAP and HPT samples the measurements were further analyzed by MAUD. Domain sizes and phase volume fractions were determined as a function of the radial direction of the samples. Alpha and Omega phases were detected in different amounts depending mostly on hydrostatic pressure and shear deformation. These transition phases can be pressure-induced during HPT processing and the results of Vickers microhardness measurements were related to the processing parameters and to the amounts of these phases.

Highlights

It is well known that severe plastic deformation (SPD) has excellent capability for grain refinement, thereby enhancing the mechanical properties of metals and alloys [1, 2]
Among the various SPD techniques recently developed, Equal-Channel Angular Pressing (ECAP) and High-Pressure Torsion (HPT) have received a great deal of attention: in the former, pure shear deformation can be repeatedly applied with no change in the cross-sectional dimensions of the sample, while the latter consists of the simultaneous application of pressure and shear
The current paper describes a study of the correlations between local mechanical properties, indirectly measured by microhardness, and synchrotron radiation taken along the radii of the various ECAP + HighPressure Torsion (HPT) severely deformed samples

Summary

Introduction

It is well known that severe plastic deformation (SPD) has excellent capability for grain refinement, thereby enhancing the mechanical properties of metals and alloys [1, 2]. Ti occupies a special place among the light metals since it combines high strength with low density and high corrosion resistance; its alloys find a number of applications in the aerospace industry, chemical equipment and medical implants. Regarding this last application, SPD techniques have been successfully applied to commercially pure Ti as a strategy for increasing its tensile strength.

Results

Discussion

Conclusion