Solute lean Ti-Nb-Fe alloys: An exploratory study

• Published in: Journal of the mechanical behavior of biomedical materials Vol. 65; pp. 761 - 769
• Main Authors: Salvador, Camilo A.F., Dal Bó, Mariana R., Costa, Fernando H., Taipina, Marcia O., Lopes, Eder S.N., Caram, Rubens
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01-01-2017
• Subjects: Alloy design; Alloys - analysis; Compressive Strength; Elastic Modulus; Hot Temperature; Iron - analysis; Materials Testing; Mechanical properties; Niobium - analysis; Phase transformations; Quenching; Titanium - analysis; Titanium alloys; Mechanical properties; Titanium alloys; Phase transformations; Alloy design; Quenching
• ISSN: 1751-6161; 1878-0180
• DOI: 10.1016/j.jmbbm.2016.09.024

In this study, we explored the Ti-Nb-Fe system to find an optimal cost-effective composition with the lowest elastic modulus and the lowest added Nb content. Six Ti-(31-4x)Nb-(1+0.5x)Fe ingots were prepared and Nb was substituted with Fe, starting at Ti-31Nb-1.0Fe and going up to Ti-11Nb-3.5Fe (wt%). The ingots were subjected to cold rolling, recrystallization and solution treatment, followed by water-quenching (WQ), furnace cooling (FC) or step-quenching to 350°C, which caused massive formation of isothermal ω phase. All the water-quenched alloys displayed athermal ω phase, which is apparently the result of fully collapsed β phase. The Fe content improved the compressive strength of the alloys. In the FC alloys, substitution with Fe favored the formation of α phase instead of ω phase, giving rise to a solute-rich β phase with a lattice parameter of 0.3249nm. Among the FC alloys, the lowest modulus of 83±4GPa was obtained in the Ti-19Nb-2.5Fe alloy, which exhibited fine and well dispersed α precipitation and absence of ω phase. DSC experiments indicated that the experimental alloys showed varying phase stability during heating.
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•Six solute lean Ti-Nb-Fe alloys (from 31Nb-1.0Fe to 11Nb-3.5Fe) were prepared.•Omega phase was detected via TEM among all solution-treated, water-quenched alloys.•Fe enhances mechanical strength due to solid solution effect.•The experimental alloys showed varying phase stability during heating.•On continuous cooling, Fe favors the α phase formation instead of iso ω phase.