The main aim of this study was the fabrication of functionally graded materials for biomedical applications. Samples with gradient porosities were prepared by a two-stage powder metallurgy method. The internal and external zones of both samples were composed of different phases and pore structures. The phase compositions, microstructures, porosities, and microhardness of the sintered samples were analysed. The results revealed successful fabrication of materials with gradient porosities by the powder metallurgy method, and the transition zone (formed by diffusion) between the external and internal zones was found to be permanent. The Rietveld refinement analysis showed that the production method and atomic radii of the elements used in the synthesis influenced the material structure. This paper is part of a Thematic Issue on The Crystallographic Aspects of Metallic Alloys.

The study presents the results of the influence of high-energy ball-milling time on the structure of the new β -type Ti–Ta–Nb–Zr alloys for biomedical applications. Initial elemental powders were mechanically alloyed in a planetary high-energy ball mill at different milling times (from 10 to 90 h). Observation of the powder morphology after various stages of milling leads to the conclusion that with the increase of the milling time the size of the powder particles as well as the degree of aggregation change. Clear tendency of crystalline size reduction at every stage of the grinding process is clearly observed. The X-ray diffraction results confirmed the formation of β phase during high-energy ball milling of the precursor mixture of Ti, Ta, Nb, and Zr. The Rietveld refinement method has shown that both the production method and the atomic radii of the elements used in the mechanical synthesis have influence on the structure. Furthermore, it was found that a broadening of the diffraction peaks with increase of the milling time results from an increase in the crystallites dispersion and an enlargement in the lattice distortion. The results indicate that this technique is a powerful and high productive process for preparing new β -titanium alloys with nanocrystalline structure and appropriate morphology.

In the present study, the structure and porosity of binary Ti–35Zr (wt.%) alloy were investigated, allowing to consider powder metallurgy as a production method for new metallic materials for potential medical applications. The porous Ti–Zr alloys were obtained by milling, cold isostatic pressing and sintering. The pressure during cold isostatic pressing was a changing parameter and was respectively 250, 500, 750 and 1000 MPa. The X-ray diffraction study revealed only the α phase, which corresponds to the Ti–Zr phase diagram. The microstructure of the Ti–35Zr was observed by optical microscopy and scanning electron microscopy. These observations revealed that the volume fraction of the pores decreased from over 20% to about 7% with increasing pressure during the cold isostatic pressing. The microhardness measurements showed changes from 137 HV0.5 to 225 HV0.5.