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The aim of the present work is to discuss process parameters effect on microstructure evolution and formation mechanism of ultrafine grains. As plastic deformation technique Equal Channel Angular Pressing (ECAP) method used pure Ti G4 rods processed in order to obtain fine grained micro structure. Equal Chanel Angular Pressing technique was conducted at different processing route, process temperature, pressing velocity with an orthogonal design to critically evaluate the significance of these process parameters with their different levels. The microstructure was observed with optical and electron back scattering diffraction (EBSD) microscope. The mechanical properties were tested with tensile, hardness tests and phase is controlled with XRD analysis.

Two different processing routes are used to investigate the microstructure and strength of commercial purity (CP) titanium of grade 4 processed by equal‐channel angular pressing (ECAP). In the combined temperature (CT) route, the specimens are pressed at 723 K in the first pass and at 373 K in the second pass, but in the warm temperature (WT) route, the specimens are pressed through two passes at 723 K. Both routes lead to an inhomogeneous microstructure with an average grain size of ≈1.5 and ≈1.7 μm after the CT and WT routes, respectively. Both routes give improved strengthening and higher hardness, but the CT route with a lower temperature step gives the highest ultimate tensile strength of ≈790 MPa. The inclusion of a lower temperature processing step may be important for optimizing the strength of CP Ti for the use in medical implants.

A biomedical b-type Ti-13Nb-13Zr (TNZ) (wt pct) ternary alloy was subjected to severe plastic deformation by means of hydrostatic extrusion (HE) at room temperature without intermediate annealing. Its effect on microstructure, mechanical properties, phase transformations, and texture was investigated by light and electron microscopy, mechanical tests (Vickers microhardness and tensile tests), and XRD analysis. Microstructural investigations by light microscope and transmission electron microscope showed that, after HE, significant grain refinement took place, also reaching high dislocation densities. Increases in strength up to 50 pct occurred, although the elongation to fracture left after HE was almost 9 pct. Furthermore, Young's modulus of HE-processed samples showed slightly lower values than the initial state due to texture. Such mechanical properties combined with lower Young's modulus are favorable for medical applications. Phase transformation analyses demonstrated that both initial and extruded samples consist of a¢ and b phases but that the phase fraction of a¢ was slightly higher after two stages of HE.

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