Non-Isothermal Oxidation Behaviors and Mechanisms of Ti-Al Intermetallic Compounds

Abstract

Non-isothermal oxidation is one of the important issues for the safe application of Ti-Al alloys, so this study aimed to illustrate the non-isothermal oxidation behaviors and the corresponding mechanisms of a TiAl-based alloy in comparison with a Ti3Al-based alloy. The non-isothermal oxidation behaviors of Ti-46Al-2Cr-5Nb and Ti-24Al-15Nb-1.5Mo alloys in pure oxygen were comparatively investigated with a thermogravimetry-differential scanning calorimetry (TGA/DSC) simultaneous thermal analyzer heating from room temperature to 1450 °C with a heating rate of 40 °C/min. When the temperature rose above 1280 °C, the oxidation rate of the Ti-46Al-2Cr-5Nb alloy sharply increased and exceeded that of the Ti-24Al-15Nb-1.5Mo alloy owing to the occurrence of internal oxidation. When the temperature was higher than 1350 °C, the oxidation rate of the Ti-46Al-2Cr-5Nb alloy decreased obviously due to the generation of an oxygen-barrier β-Al2TiO5-rich layer by a chemical reaction between Al2O3 and TiO2 in the oxide scale. Based on Wagner’s theory of internal oxidation, the reason for the occurrence of internal oxidation in the Ti-46Al-2Cr-5Nb alloy is the formation of the α phase in the subsurface, while no internal oxidation occurred in the Ti-24Al-15Nb-1.5Mo alloy due to the existence of the β phase in the subsurface with the enrichment of Nb and Mo.

Isothermal Oxidation Behavior of Novel Al2O3 / NiCrAlY / Ti3Al System at 850�C

“…That enforces continuous development of new generations of TiAl alloys with improved properties (low density, high specific strength and melting temperature, good creep resistance, excellent fireproof performance) in comparison with Ti-alloys which replaced Nisuperalloys [2,3]. Both conventional Ti-alloys and titanium aluminide alloys, especially in alpha form with rich titanium content 2-Ti3Al, show poor oxidation and corrosion resistance at elevated temperatures in air as well as in marine environments at ambient temperature [1][2][3][4][5][6]. Choice of titanium richer alloys, TiAl (γ phase), Ti2AlNb (o-ortho phase) and 2-Ti3Al alloys, is ruled by their superior mechanical characteristics [7,8].…”

High-temperature oxidation behavior of a cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy

“…But, when the temperature exceeds 800 °C, the continuous and dense Al 2 O 3 protective oxide film cannot be generated on the surface, and instead a mixed oxide consisting of TiO 2 and Al 2 O 3 is formed. TiO 2 has a loose structure and large oxygen permeability, which cannot prevent the diffusion of O atoms, resulting in insufficient oxidation resistance; thus, restricting their further application [5][6][7][8] . Therefore, enhancing the oxidation resistance of TiAl alloys above 800 °C has become an urgent problem [9] .…”

Special Issue: Recent Advances in Corrosion Science

“…The search for alloying additives enhancing the corrosion resistance without sacrificing the desired characteristics continues, intending to reduce alloy corrosion rate and bring measurable economic profits. Within this Special Issue, you will find multiple original research papers strictly devoted to this issue for both ferrous [2][3][4] and non-ferrous metals [5][6][7][8]. The influence of novel microscopy tools, which enable the direct observation of local corrosion processes, cannot be overestimated.…”