Speaker
Description
High entropy alloys have attracted considerable attention in the past decade due to their excellent mechanical properties and thermal stability which often exceed values of those of their constituting species as well as commonly investigated intermetallic phases. Titanium aluminides are a class of light-weight high-temperature structural materials with excellent mechanical properties and a strong application potential in the automotive and aerospace industries.
In this contribution, we report on Density Functional Theory-based calculation on a model high entropy/multi-component alloy with Ti and Al as principle elements, and Nb, V and Mo or Mn yielding a 5-component equimolar solid solution. In our investigations, we considered bcc and C14 Laves phases, inspired by experimental observations. We have estimated most-likely decomposition products of those systems, considering all decomposition routes (i.e. into combinations of unary, binary, ternary and quaternary bcc and C14 alloys). The temperature was included via entropy of mixing of a solid solution. Our results suggest that while the Ti-Al-Nb-V-Mo remains stable in the bcc solid solution at temperatures above ~1000K, the Ti-Al-Nb-V-Mn system was predicted to exhibit a significant driving force for decomposition even at temperatures above 1200K. In this case, however, the decomposition products would include the Mn-rich C14 Laves phase. These predictions have been corroborated by experimental studies. We will also discuss methodological aspects related to dealing with multi-component disordered systems at the DFT level. Finally, we will show the interplay between the chemical complexity, chemical composition and local structural distortions of those multi-component alloys. The concomitant experimental verification was performed by examination and analysis methods with a resolution ranging from macroscopic to atomic scales.
| Speaker Country | Austria |
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