First-principles study on mechanical properties and dislocation core in BCC refractory high-entropy alloys

Tsuru, Tomohito

no journal, , 

Refractory body-centered cubic (BCC) high-entropy alloys (HEAs) have excellent mechanical properties and their features differ significantly depending on constituent elements. For example, BCC-HEAs containing specific elements show an excellent balance between high strength and elongation and unique slip behavior. Therefore, it is essential to understand the atomic-level depiction of defect structures considering the effects of the constituent elements to elucidate the origin of the unique mechanical properties of HEA. Especially, a detailed exploration of dislocation core structure and motion should be the key to identifying the mechanical properties. In the present study, we focused on two BCC-HEAs with different features and chose VNbMoTaW and TiZrNbHfTa as widely-discussed alloy systems in the community. We expected that the origin of the difference in mechanical properties was caused by the local lattice distortion, elastic properties, and short-ranged order (SRO) formation, which should be derived from the existence of the group IV elements with a sufficient concentration. We investigate the differences of these properties and the dislocation core features between two BCC-HEAs using the first-principles calculations. As a result, the mean square displacement of TiZrNbHfTa was quite large. This significant lattice distortion originates from the group IV elements, but the SRO formation does not influence the value. Furthermore, the dislocation core of TiZrNbHfTa tends to expand widely, which is totally different from most conventional BCC metals and alloys. The unique core structure and slip behavior of TiZrNbHfTa are also caused by highly concentrated group IV elements.

Twinning and detwinning in AZ31 alloy at 20K studied by in-situ neutron diffraction

Gong, W.; Harjo, S.; Kawasaki, Takuro; Aizawa, Kazuya; Tsuji, Nobuhiro*

no journal, ,