Heterogeneous Precipitation of the α-Phase in Ti15Mo Alloy Subjected to High Pressure Torsion

K. Barthaa, J. Stráskýa, P. Harcubaa, I. Semenovab, V. Polyakovab, M. Janečeka aDepartment of Physics of Materials, Charles University, Ke Karlovu 5, 121 16, Prague, Czech Republic bInstitute of Physics of Advanced Materials, UFA State Aviation Technical University, K. Marx Street 12, 450 000, Ufa, Russia

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Ti15Mo alloy is a binary metastable beta titanium alloy with excellent mechanical properties and biocompatibility. Therefore, it can potentially replace the most commonly used Ti6Al4V alloy in biomedical applications. Further processing of the alloy by the methods of severe plastic deformation provides an opportunity to achieve exceptional grain refinement and to enhance mechanical properties. Another way how to increase the strength of the alloy is thermomechanical processing which leads to the formation of the α-phase. α-phase is known to precipitate heterogeneously, in particular at grain boundaries. Refinement of parent β matrix therefore affects the size and the morphology of α precipitates. Ultrafine grained Ti15Mo alloy was processed by high pressure torsion. The precipitation behavior of ultrafine grained and benchmark coarse-grained material during isothermal ageing was investigated by ex situ scanning electron microscopy. In the coarse-grained material the α-phase precipitates both as grain boundary α-phase and as acicular α-phase inside the β-grains. On the other hand, in ultrafine grained alloy, only equiaxed sub-micrometer α particles precipitated at dense network of grain boundaries.

DOI:10.12693/APhysPolA.134.790 PACS numbers: 61.66.Dk, 61.72.Mm, 64.60.My, 64.70.kd