On the influence of alloy composition on the oxidation performance and oxygen-induced phase transformations in Ti–(0–8) wt%Al alloys

• Published in: Journal of materials science 2016-04, Vol.51 (8), p.3684-3692
• Main Authors: Samimi, P, Brice, D. A, Banerjee, R, Kaufman, M. J, Collins, P. C
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum; Aluminum base alloys; Aluminum oxide; Binary systems; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Combinatorial analysis; Composition; Crystallography and Scattering Methods; Exposure; exposure duration; Heat treatment; Intermetallics; Materials Science; Morphology; Original Paper; Oxidation; Oxidation tests; Oxidation-reduction reaction; Oxides; phase transition; Phase transitions; Polymer Sciences; Scale (corrosion); Solid Mechanics; Titanium; Titanium aluminides; Titanium base alloys; Titanium dioxide
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-015-9681-x

Adopting a high-throughput combinatorial approach, a compositionally graded Ti–xAl (0 ≤ x ≤ 8 wt%) specimen was prepared to conduct a rapid systematic investigation of the influence of composition and exposure time on the oxidation performance of the titanium-rich section of the binary Ti–Al system. The compositionally graded specimen was solution heat treated and subjected to oxidation tests at 650 °C for different exposure times. The morphology, structure, and composition of the oxide scale as well as the microstructural changes in the base material were studied across the entire composition range, using a suite of characterization techniques. The observations revealed the presence of Al₂O₃ in the topmost layer of the oxide scale in addition to TiO₂, indicating its early formation during oxidation. An increase in Al concentration improves the scaling rate of Ti; however, this is observed only for extended exposure times (i.e., 50 and 100 h), and a parabolic oxidation law is obeyed in the composition-time domain. The formation of the α₂ phase (Ti₃Al) also takes place for relatively higher Al contents (i.e., 8 wt%).