TY - JOUR

T1 - Mechanism of room-temperature superplasticity in ultrafine-grained Al–Zn alloys

AU - Song, Z.Z.

AU - Niu, R.M.

AU - Cui, X.Y.

AU - Bobruk, Elena V.

AU - Мурашкин, Максим Юрьевич

AU - Еникеев, Нариман Айратович

AU - Gu, Ji

AU - Song, Min

AU - Bhatia, Vijay

AU - Ringer, Simon P.

AU - Валиев, Руслан Зуфарович

AU - Liao, X.Z.

PY - 2023/3/1

Y1 - 2023/3/1

N2 - Superplastic deformation of polycrystalline materials is usually accommodated by diffusion-assisted grain boundary (GB) sliding at high temperatures. Lowering the temperature requirement for commercial superplastic forming enables green and cost-effective manufacturing. Recently, room-temperature (RT) superplasticity was realized in ultrafine-grained Al–Zn based alloys, but the underlying mechanism remains unclear. Here, we conducted in-situ tensile straining and post-mortem electron microscopy characterization, and atomistic density functional theory simulation to understand the RT superplasticity of an Al–15 Zn (at%) alloy. Results showed that the superplasticity is achieved by GB sliding and grain rotation, assisted by the continuous diffusion of Zn. In-situ observations showed Zn atoms diffusing from within grains to GBs, resulting in a Zn nanolayer at the GBs that acts as a solid lubricant to decrease the energy barrier of GB sliding. This research advances our understanding of diffusion-assisted deformation mechanism that is a prerequisite for the rational design of new materials with RT superplasticity.

AB - Superplastic deformation of polycrystalline materials is usually accommodated by diffusion-assisted grain boundary (GB) sliding at high temperatures. Lowering the temperature requirement for commercial superplastic forming enables green and cost-effective manufacturing. Recently, room-temperature (RT) superplasticity was realized in ultrafine-grained Al–Zn based alloys, but the underlying mechanism remains unclear. Here, we conducted in-situ tensile straining and post-mortem electron microscopy characterization, and atomistic density functional theory simulation to understand the RT superplasticity of an Al–15 Zn (at%) alloy. Results showed that the superplasticity is achieved by GB sliding and grain rotation, assisted by the continuous diffusion of Zn. In-situ observations showed Zn atoms diffusing from within grains to GBs, resulting in a Zn nanolayer at the GBs that acts as a solid lubricant to decrease the energy barrier of GB sliding. This research advances our understanding of diffusion-assisted deformation mechanism that is a prerequisite for the rational design of new materials with RT superplasticity.

KW - Al-Zn

KW - DFT

KW - Grain boundary sliding

KW - High resolution HAADF-STEM

KW - In-situ SEM

KW - Room-temperature superplasticity

UR - https://www.mendeley.com/catalogue/7f0345e0-71d2-334e-bd0e-cfa8ef43e440/

U2 - 10.1016/j.actamat.2023.118671

DO - 10.1016/j.actamat.2023.118671

M3 - Article

VL - 246

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

M1 - 118671

ER -