Sheng, Ruixin | Engineering Papers

DOE OSTI2022

Viscoelasticity-induced structure anisotropy in amorphous materials

Viscoelasticity-induced structural change in Zr 55 Cu 30 Ni 5 Al 10 metallic glass (Zr-MG) and amorphous selenium (a-Se) is investigated using synchrotron X-ray diffraction. By analyzing the two-dimensional diffraction pattern, two types of structural anisotropy with the feature of the residual elastic strain or heterogeneous intensity of diffraction rings are revealed. The origin of the structural anisotropy is attributed to the topological rearrangement in the Zr-MG and conformation rearrangement in the a-Se. In conclusion, our findings bring a structural identity to the phenomenological structureless deformation defect widely used in different amorphous materials.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Charge transfer effect on local lattice distortion in a HfNbTiZr high entropy alloy

We report it is often assumed that atoms are hard spheres in the estimation of local lattice distortion (LLD) in high-entropy alloys (HEAs). However, our study demonstrates that the hard sphere model misses the key effect, charge transfer among atoms with different electronegativities, in the understanding of the severely distorted local structure in the body-centered cubic (BCC) HfNbTiZr HEA. Through the characterization and simulations of the local structure of the HfNbTiZr HEA, we found that the LLD regions in HfNbTiZr have larger average size compared with face-centered cubic (FCC) HEAs, but the magnitude of LLD significantly varies from one atomic site to another because of electron transfer from larger atoms, Hf and Zr, to smaller ones, Nb and Ti. Our finding may form the basis for the design of high performance HEAs through tuning their site-to-site chemical heterogeneity.

36 MATERIALS SCIENCE↗