Microstructural Characterization of Ti-Nb-(Fe-Cr) Alloys Obtained by Powder Metallurgy

摘要

Ti β-alloys based on the Ti-Nb alloy system exhibit growing interest in the biomaterial community. Theaddition of small amounts of Fe and Cr further increases β-phase stability, improving the properties ofTi-Nb alloy. Production of such alloys by powder metallurgy (PM) starting from elemental powders hasthe problem of lacking homogeneity due to restricted solid state diffusion. To improve mixing anddiffusion of the elements mechanical alloying is used. This paper studies the microstructuralcharacterization and mechanical properties obtained by bending tests of Ti-Nb-(Fe-Cr) alloys obtainedby conventional PM with elemental powder mixture and mechanical alloying. The mechanical alloyingallows a much more homogeneous composition and particle morphology, characterized by roundedand significantly enlarged powder particles. In the sintered samples two phases appear, namely alphaand beta phase. The α phase appears at the grain boundaries and in lamellae growing from the edgeinward, formed mainly by Ti and lower Nb content than nominal. The beta phase is enriched with Nb,Fe and Cr. The addition of the both latter elements increases considerably mechanical properties ofTi-Nb alloys, providing increased ductility.