Effects of double-aging heat-treatments on the microstructure and mechanical behavior of an Nb-modified Ti-5553 alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 743; pp. 716 - 725
• Main Authors: Salvador, Camilo A.F., Opini, Victor C., Mello, Mariana G., Caram, Rubens
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 16-01-2019; Elsevier BV
• Subjects: Aging; Aging (metallurgy); Aircraft components; Aircraft industry; Alloys; Compression tests; Electron microscopy; Embryos; Grain boundaries; Hardness; Heat treatment; Mechanical properties; Microstructure; Phase transformation; Phase transitions; Plasticity; Scanning electron microscopy; Stress/strain measurements; Titanium alloys; Titanium base alloys; Transmission electron microscopy; X-ray diffraction; DF; BF; APT; XRD; Electron microscopy; Hardness; STEM; HRTEM; Titanium alloys; Phase transformation; LAGB; HRSTEM; FFT; SAD; Plasticity; Stress/strain measurements; TEM; HAADF
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2018.11.086

Ti-5553 and related alloys are known as important structural alloys in the aircraft industry. In this work, the effect of double aging heat-treatments on the phase transformations and mechanical behavior of an Nb-modified Ti-5553 alloy (Ti-12Nb-5Al-5V-3Cr-0.5Fe wt%) was investigated by X-ray diffraction, scanning, and transmission electron microscopy. Results show the phase transformation sequence is altered with the time spent at the first aging stage. After 3 h at 350 °C, isothermal ω-phase is extensively formed throughout the β-matrix, while after 8 h, α-phase embryos were detected. The first stages of α-phase formation in the modified alloy seem to be influenced both by the presence of ω particles and low-angle grain boundaries. Microstructures resultant of the first stages of aging change the response to the second stage, performed at 525 °C and 600 °C, for 2 h. The final microstructure obtained for the modified alloy (Ti-12Nb) after the second stage of aging diverge from the original Ti-5553 alloy subjected to the same heat-treatment. Finally, tensile and compression tests indicate Ti-12Nb is a viable substitute for Ti-5553, with comparable strength and slightly lower ductility after double aging.
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