Determination of atomic-scale structure and compressive behavior of solidified AlxCrCoFeCuNi high entropy alloys

• Published in: International journal of mechanical sciences 2020-04, Vol.171, p.105389, Article 105389
• Main Authors: Bahramyan, Mehran, Taherzadeh Mousavian, Reza, Brabazon, Dermot
• Format: Article
• Language: English
• Subjects: Amorphous structure; BCC structure; Compression test; High-Entropy alloys; Molecular dynamics simulation; Solidification
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2019.105389

•Solidification of AlxCoCrFeCuNi HEAs was studied with a focus between 2200 K to super-heating temperatures of HEAs.•A higher cooling rate from experimental not only avoid formation of nano-precipitates but also form BCC structure.•Aluminum addition caused a reduction in super-heating temperature and mobility of nickel and copper atoms.•Compressive test shows that the addition of Al could results to lower UCS. The atomic configurations play a key role in predicting the solidification process of high-entropy alloys (HEAs). The atomic scale structures of AlxCrCoFeCuNi (x = 0.5, 1.5, 3.0) HEAs that emerge during solidification with a cooling rate of 12 × 109 (K/s) are evaluated using molecular dynamics (MD) simulation. While BCC (body-centered cubic) structure is obtained for Al0.5CrCoFeCuNi and Al1.5CrCoFeCuNi where lattice distortion increases with increasing aluminum fraction from x = 0.5 to x = 1.5, for Al3.0CrCoFeCuNi, an amorphous structure is formed under the same cooling rate. The diffusion coefficient of all the elements at 2200 K and the super-heating temperature of each alloy are evaluated to explain the disordering mechanism due to aluminum addition, which affects both the aluminum mobility and diffusion of the constituent atoms in the HEA. Finally, the compression behavior of all the three HEAs was studied to show the effect of crystalline structure on the stress fluctuation. It was found that phase transformation induced plasticity occurred which led to a secondary hardening of crystalline alloys after ultimate compressive strength (UCS).