Mechanism of room-temperature superplasticity in ultrafine-grained Al–Zn alloys. (1st March 2023)

• Record Type: Journal Article
• Authors: Song, Zizheng; Niu, Ranming; Cui, Xiangyuan; Bobruk, Elena V.; Murashkin, Maxim Yu.; Enikeev, Nariman A.; Gu, Ji; Song, Min; Bhatia, Vijay; Ringer, Simon P.; Valiev, Ruslan Z.; Liao, Xiaozhou
• Is Part Of: Acta materialia. Volume 246(2023)
• Publication Date: 2023-03-01
• Subjects: Room-temperature superplasticity -- Al-Zn -- In-situ SEM -- High resolution HAADF-STEM -- DFT -- Grain boundary sliding; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2023.118671
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: 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. Graphical abstract: Image, graphical abstract