By the results of X-ray analysis, microstructural analysis, nanohardness and elastic modulus measurements it was defined that non-equilibrium phases during the process of crystallization are formed in the titanium-niobium alloy with 40wt.% of Nb. The minimum of non-equilibrium phases is formed at the Ti-40wt.% Nb alloy. The uniform grain structure, which consists of β-phase grains with the minimum of elastic modulus, is formed in the alloy ingot. Such structure and complex of properties allows using this alloy for severe plastic deformation.
The phase transformations of the alloy Ti-40 mas % Nb after tempering and severe plastic deformation are studied. The phase transformations of the alloy according to the type and conditions of external influences are analyzed using methods of XRD, SEM and optical metallography. It is determined that inverse phase transformation of the metastable α''-phase to equilibrium β-phase is carried out after severe plastic deformation. Complete phase transformation α'' → β is typical for the mode, which consists of three pressing operation with the change of the loading axis in cramped conditions, followed by a multi-pass rolling in grooved rolls.
Porosity, values of nanohardness and Young’s modulus of the specimens obtained with the method of selective laser melting were measured with optical methods, scanning electron microscopy and Nano Hardness Tester NHT-S-AX-000X device for measuring physicomechanical properties. Ti-45wt%Nb powder obtained with mechanical alloying was used for selective laser melting. The results have shown that increased heat input due to the laser power growth up to 80 W and scanning speed decrease down to 40 mm/s decreases the porosity of the specimen. The nanohardness average value is not sensitive to the changes of scanning modes in the investigated range. The Young’s modulus decreases with energy input increase.
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