Deformation Structures of Pure Titanium during Shear Deformation
- PDF / 881,242 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 94 Downloads / 280 Views
INTRODUCTION
IN recent years, commercial pure (CP) Ti processed by severe plastic deformation (SPD) methods has attracted growing interest.[1–6] This is based on the great potential of CP-Ti for applications such as medical implants with better biocompatibility and containing no toxic alloying elements.[1] It has been proved that the mechanical properties of CP-Ti can be significantly improved by SPD, so that they are comparable with those of conventional Ti-6Al-4V alloy.[7] The yield strength of ultrafine-grained (UFG) CP-Ti, fabricated by two-step SPD or equal channel angular pressing (ECAP) plus cold rolling, has been increased to 900 to 1000 MPa.[7,8] Yield strength as high as 1250 MPa has been achieved for CP-Ti with an average grain size of 47 nm, processed by hydrostatic extrusion (HE).[6] The conventional Hall–Petch equation has been found not to be applicable to nanostructured CP-Ti.[8] Clearly, the understanding of these properties should be based on its unique microstructure and the process of grain refinement. In the last few years, much work has been done to characterize the nanostructures of UFG Ti, mainly by transmission electron microscopy (TEM) and X-ray Y.J. CHEN, Postdoctoral Researcher, and H.J. ROVEN, Professor, are with the Department of Materials Technology, The Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway. Contact e-mail: [email protected] Y.J. LI and S. DUMOULIN, Researchers, and J.C. WALMSLEY, Senior Researcher, are with Materials and Chemistry, SINTEF, 7491 Trondheim, Norway. This article is based on a presentation given in the symposium entitled ‘‘Mechanical Behavior of Nanostructured Materials,’’ which occurred during the TMS Spring Meeting in San Francisco, CA, February 15–19, 2009, under the auspices of TMS, the TMS Electronic, Magnetic, and Photonic Materials Division, the TMS Materials Processing and Manufacturing Division, the TMS Structural Materials Division, the TMS Nanomechanical Materials Behavior Committee, the TMS Chemistry and Physics of Materials Committee, and the TMS/ASM Mechanical Behavior of Materials Committee. Article published online November 24, 2009 METALLURGICAL AND MATERIALS TRANSACTIONS A
diffraction. Zhu and co-workers have systematically investigated the hierarchy of defect structures including grain and subgrain structure, dislocation and dislocation cells (DCs), and grain boundaries in nanostructured CP-Ti.[8] However, due to the limited examination volume of TEM samples, the knowledge of the distributions of grain boundaries and misorientations of grain and subgrain structures has been limited. Electron backscatter diffraction (EBSD) has been widely employed to characterize quantitatively the fractions of low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs), distributions of grain sizes and misorientation, and the evolution of texture and development of substructure in Mg alloys,[9] Al alloys[10] and steels,[11] after plastic deformation. However, dislocations and dislocation structures, LAGBs with misorien
Data Loading...
