Alpha phase precipitation in Ti-30Nb-1Fe alloys – phase transformations in continuous heating and aging heat treatments

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 677; pp. 222 - 229
• Main Authors: da Costa, Fernando Henrique, Salvador, Camilo A.F., de Mello, Mariana G., Caram, Rubens
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20-11-2016; Elsevier BV
• Subjects: Aging (metallurgy); Aging heat treatments; Alloys; Diamond pyramid hardness; Differential scanning calorimetry; Diffusion coefficient; Diffusion rate; Elastic properties; Heat measurement; Heat treating; Heat treatment; Heating rate; Mechanical properties; Microstructure; Modulus of elasticity; Phase transformations; Phase transitions; Precipitates; Tensile tests; Titanium alloys; Titanium base alloys; Transmission electron microscopy; X-ray diffraction; Titanium alloys; Differential scanning calorimetry; Aging heat treatments; Phase transformations
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2016.09.023

Microstructure and mechanical properties of β metastable Ti-30Nb and Ti-30Nb-1Fe alloys subjected to different aging heat treatments were investigated. Various temperatures and heating rates were employed in order to determine their influence on α phase precipitation. The alloys were characterized by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning and transmission electron microscopy. Several mechanical properties were evaluated, such as Vickers hardness and elastic modulus, and tensile tests were also performed. The results indicate that the addition of Fe reduces the α phase precipitation and ω dissolution temperatures, although ω phase was still detected in Ti-30Nb-1Fe aged at 400°C. The addition of Fe caused refinement of α phase precipitates, probably due to the higher diffusion coefficient of Fe. As for the influence of the heating rate, 2 and 30°C/min did not cause significant microstructural changes. Finally, α phase refinement in Ti-30Nb alloy was favored by aging at 550°C, at a heating rate of 600°C/min.