Decision Science Driven Selection of High-Temperature Conventional Ti Alloys for Aeroengines

Abstract

Near-α Ti alloys find themselves in advanced aeroengines for applications of up to 600 °C, mainly as compressor components owing to their superior combination of ambient- and elevated-temperature mechanical properties and oxidation resistance. We evaluated, ranked, and selected near-α Ti alloys in the current literature for high-temperature applications in aeroengines driven by decision science by integrating multiple attribute decision making (MADM) and principal component analysis (PCA). A combination of 12 MADM methods ranked a list of 105 alloy variants based on the thermomechanical processing (TMP) conditions of 19 distinct near-α Ti alloys. PCA consolidated the ranks from various MADMs and identified top-ranked alloys for the intended applications as: Ti-6.7Al-1.9Sn-3.9Zr-4.6Mo-0.96W-0.23Si, Ti-4.8Al-2.2Sn-4.1Zr-2Mo-1.1Ge, Ti-6.6Al-1.75Sn-4.12Zr-1.91Mo-0.32W-0.1Si, Ti-4.9Al-2.3Sn-4.1Zr-2Mo-0.1Si-0.8Ge, Ti-4.8Al-2.3Sn-4.2Zr-2Mo, Ti-6.5Al-3Sn-4Hf-0.2Nb-0.4Mo-0.4Si-0.1B, Ti-5.8Al-4Sn-3.5Zr-0.7Mo-0.35Si-0.7Nb-0.06C, and Ti-6Al-3.5Sn-4.5Zr-2.0Ta-0.7Nb-0.5Mo-0.4Si. The alloys have the following metallurgical characteristics: bimodal matrix, aluminum equivalent preferably ~8, and nanocrystalline precipitates of Ti3Al, germanides, or silicides. The analyses, driven by decision science, make metallurgical sense and provide guidelines for developing next-generation commercial near-α Ti alloys. The investigation not only suggests potential replacement or substitute for existing alloys but also provides directions for improvement and development of titanium alloys over the current ones to push out some of the heavier alloys and thus help reduce the engine’s weight to gain advantage.

Strategic Selection of Refractory High-Entropy Alloy Coatings for Hot-Forging Dies by Applying Decision Science

“…Figure 1 presents a flowchart of the strategic selection of RHEAs for coating hot-forging dies by applying decision science. The decision science-driven selection methodology is similar to the selection of Ti-containing high-entropy alloys for aeroengine turbine applications and the selection of high-temperature conventional Ti alloys for aeroengines [20,28]. It consists of three key routines: (i) literature data (compilation of refractory high-entropy alloy-based coatings for hot-forging dies); (ii) ranking (ranking by MADM methods); and (iii) analyses (rank consolidation by PCA and interpretation).…”

“…This comprehensive set of methods enables a thorough evaluation of the RHEAs and facilitates a robust ranking based on their suitability for the intended application. The MADM methods were soft-coded in Microsoft Excel (Version 2311) [28].…”

“…This method allows us to identify groupings or clusters based on similarity criteria. All the analyses were conducted using the commercial software Minitab ® 21 [28].…”

“…It is crucial to emphasize that generating data on all the properties (such as wear resistance, strength, fatigue properties, fabricability, coating methods, bonding characteristics, the necessity of a multi-material gradient layer, etc.) for every available RHEA in the current literature is a time-consuming, laborious, and costly endeavor [28]. Moreover, not all the properties mentioned above are documented for every RHEA in the literature; only a few common properties of most RHEAs are reported.…”

Microstructure and Properties in Metals and Alloys

“…A semi-empirical model for predicting the ultimate bond strength of the short-lapped-rebar splice is proposed, and it shows good agreement with tested values; the average error estimated from the proposed model is only 4.49%. R. Canumalla et al [21] evaluated, ranked, and selected near-α Ti alloys from the literature for high-temperature applications in aeroengines driven by decision science by integrating multiple attribute decision making (MADM) and principal component analysis (PCA). A combination of 12 MADM methods ranked a list of 105 alloy variants based on the thermomechanical processing (TMP) conditions of 19 distinct near-α Ti alloys.…”