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Lecture

WEB DFT study of elastic and dislocation properties of BCC High entropy alloys

Wednesday (23.09.2020)
15:15 - 15:30 S: Structural Materials 2
Part of:


High-entropy alloys (HEAs) are alloys consisting of five or more elements, in atomic composition ranging from 5-35%. These alloys exhibit a unique mechanical behavior at high temperatures because of stability gained by high configuration mixing entropy. As a result, they have immense applications in areas such as orthopedic implants, airspace, and military industry, etc. thanks to their better strength-to-weight ratios, a high degree of fracture resistance, tensile strength, and wear and oxidation resistance than conventional alloys. In the literature, face-centered cubic (fcc) HEAs have been widely investigated but few studies have been done on body-centered cubic (bcc) refractory high-entropy alloys. In this study, we have focused on bcc refractory HfNbTaTiZr HEAs to understand the free energy of formation, elastic properties, and plastic deformation by adopting the strategy similar to traditional bcc metals where the core properties of screw dislocations still proceed along ½<111> at low temperatures.

 

To study a five-component system with classical molecular dynamics (MD) no potential exists in literature, therefore, we have resorted to density functional theory (DFT). However, modeling HEAs still poses additional problems such as the formation of intermetallic phases (IM), and lattice mismatch due to local chemical environments. In this attempt, special quasi-random (SQS) approach has been used to model random alloy. Our initial results showed the elastic properties agree with the experimental results and positive formation energy indicates they are stabilized by configurational entropic term. Further, we have investigated the generalized stacking fault energies and probed the impact of local composition fluctuation on the dislocation core structure.

Speaker:
Additional Authors:
  • Dr. Sylvain Queyreau
    University of Paris 13
  • Dr. David Tingaud
    University of Paris 13
  • Dr. Mahamadou Seydou
    University of Paris 7
  • Prof. Dr. Guy Dirras
    University of Paris 13

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