Metastable β-Phase Ti–Nb Alloys Fabricated by Powder Metallurgy: Effect of Nb on Superelasticity and Deformation Behavior

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-03, Vol.55 (3), p.707-723
• Main Authors: Kalita, D., Mulewska, K., Jóźwik, I., Zaborowska, A., Gawęda, M., Chromiński, W., Bochenek, K., Rogal, Ł.
• Format: Article
• Language: English
• Subjects: Alloy powders; Alloying elements; Beta phase; Characterization and Evaluation of Materials; Chemistry and Materials Science; Deformation; Deformation effects; Deformation mechanisms; Grain boundaries; Hot pressing; Martensitic transformations; Materials Science; Mechanical alloying; Mechanical properties; Metallic Materials; Nanotechnology; Niobium base alloys; Original Research Article; Oxygen content; Powder metallurgy; Precipitates; Structural Materials; Superelasticity; Surfaces and Interfaces; Thin Films; Titanium base alloys; Titanium carbide
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-023-07285-5

This study investigates the effect of Nb concentration on the mechanical properties, superelasticity, as well as deformation behavior of metastable β -phase Ti–Nb alloys produced via powder metallurgy. The alloys were fabricated through mechanical alloying, followed by consolidation using hot pressing. The resulting microstructure comprises fine β -phase grains with TiC carbide precipitates at the grain boundaries. The study reveals non-linear variations in the values of yield strength for the manufactured materials, which were attributed to the occurrence of various deformation mechanisms activated during the loading. It was found that the mechanisms change with the increasing concentration of Nb in the manner: stress-induced martensitic transformation, twinning, slip. However, all these mechanisms were activated at a reduced concentration of Nb compared to the materials obtained by casting technology previously reported in the literature. This is most probably associated with the elevated oxygen content, which affects the stability of the parent β -phase. The study revealed that superelasticity in Ti–Nb-based alloys prepared using powder metallurgy may be achieved by reducing the content of β -stabilizing elements compared to alloys obtained by conventional technologies. In this study, the Ti–14Nb (at. pct) alloy exhibited the best superelasticity, whereas conventionally fabricated Ti–Nb alloys displayed superelasticity at an Nb concentration of approximately 26 at. pct. The developed material exhibited a non-conventional, one-stage yielding behavior, resulting in a superelastic response at significantly higher stresses compared to conventionally fabricated Ti–Nb alloys.