Sub-stoichiometry-facilitated oxidation kinetics in a δ-TixC-doped Ti-based alloy

Abstract

Titanium carbide has been widely considered as a stabilizer to alleviate the serious chemical activity of Ti-based alloys at elevated temperatures. However, a reverse effect may also take place: we show the sub-stoichiometry characteristic of δ-Ti x C can facilitate the oxidation kinetics of a Ti-6Al-4V alloy to a significant extent. In particular, oxygen atoms tend to preferentially occupy the vacant carbon sites within the Ti 2 C phase, giving rise to a higher oxidation rate. The intrinsic mechanisms were understood with a combination of ab initio simulation and experimental validation.

Direct Rolling of TiCp/Ti–6Al–4V Composite for Improved Microstructure, Mechanical Properties, and High‐Temperature Oxidation Resistance

“…The refined and compact oxides are not easy to crack during high‐temperature cyclic oxidation process, leading to better protective effect. [ 32,33 ] On the other hand, the role of matrix microstructure on oxidation resistance cannot be ignored. Different from the coarse lamellar microstructure within as‐cast composite, the bimodal microstructure within the as‐rolled composite was much more refined, as shown in Figure 2.…”

Multiscale Architecture and Superior High‐Temperature Performance of Discontinuously Reinforced Titanium Matrix Composites

“…Environmentally expedited degradation, especially high‐temperature oxidation, is another critical factor that governs the service life‐time of metallic materials at elevated temperatures. [ 117 ] Decades of effort in the oxidation investigation of conventional Ti‐ and TiAl‐based alloys has addressed that the main goal to promote oxidation resistance is to suppress the formation of fast‐growing porous oxides (such as titania), while simultaneously facilitating the formation of dense and protective oxides (such as alumina, silica, and chromia). [ 118 ] Obviously, the introduction of ceramic reinforcements, regardless of their distribution, enables the improvement of oxidation resistance because of the alleviation of nominal chemical activity.…”

“…[ 118 ] Obviously, the introduction of ceramic reinforcements, regardless of their distribution, enables the improvement of oxidation resistance because of the alleviation of nominal chemical activity. [ 117 ] The first fundamental question thus requires elucidation is that: what is structurally unique of reinforcement network in improving the oxidation resistance?…”

“…DFT image: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/). [ 117 ] Copyright 2019, The Authors, published by Springer Nature. MD image: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/).…”

Natural-mixing guided design of refractory high-entropy alloys with as-cast tensile ductility

“…Fig.S16|Assessments of oxidation resistance at 600, 800, and 1000 o C for 2 h. Although complete understandings of oxidation resistance do require long-term kinetic analyses and sometimes involve more aggressive conditions30 , the initial stage of thermal oxidation can still be employed to rationally elucidate the underlying mechanisms31 , especially when earlystage catastrophic oxidation occurs. After being oxidized at 600, 800, and 1000 o C for 2 h it is recognized from the macroscopic morphologies (comparatively shown in a, b, and c) that the Ti38V15Nb23Hf24 RHEA demonstrates decent adherence between oxide scale and its substrate with almost no mechanical spallation taking place even at 1000 o C. In contrast, evident spallation is seen in the Ti25V25Nb25Hf25 RHEA at 800 o C (see the red arrows).…”