High temperature strength retention of Cu/Nb nanolaminates through dynamic strain ageing

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:799

Article

Liu, Zhilin^1,2  Snel, J.²  Boll, T.^3,4  Wang, J. Y.^2,5  Monclus, M. A.²  Molina-Aldareguia, J. M.²  LLorca, J.^2,5 

[1] Cent South Univ, Coll Mech & Elect Engn, Light Alloy Res Inst, Changsha 410083, Peoples R China

[2] IMDEA Mat Inst, C Eric Kandel 2, Madrid 28906, Spain

[3] Inst Appl Mat IAM WK, D-76344 Eggenstein Leopoldshafen, Germany

[4] Karlsruhe Inst Technol, Karlsruhe Nano Micro Facil, D-76344 Eggenstein Leopoldshafen, Germany

[5] Univ Politecn Madrid, Dept Mat Sci, ETS Ingn Caminos, Madrid 28040, Spain

关键词: Metallic nanolaminates;    Dynamic strain ageing;    High temperature deformation;    Atom-probe tomography;   

DOI  :  10.1016/j.msea.2020.140117

来源: Elsevier

【 摘 要 】

The mechanical properties of Cu/Nb metallic nanolaminates with different layer thickness (7, 16, 34 and 63 nm) were studied by means of micropillar compression tests from room temperature to 400 degrees C. Both strain-rate jump and constant strain rate tests were carried out and they showed evidence of dynamic strain ageing in the nanolaminates with 7, 16 and 34 nm layer thickness deformed at 200 degrees C. Dynamic strain ageing was accom-panied by a reduction of the strain rate sensitivity to 0, high strength retention at 200 degrees C and the development of shear localization of the deformation at low strains (5%-6%) that took place along the Nb layers in the nano laminates. Atom probe tomography of the deformed specimens revealed the presence of O in solid solution in the Nb layers but not in the Cu layers. Thus, diffusion of O atoms to the mobile dislocations in Nb was found to be the origin of the dynamic strain ageing in the Cu/Nb nanolaminates around 200 degrees C. This mechanism was not found at higher temperature (400 degrees C) because deformation was mainly controlled by stress-assisted diffusion in the Cu layers. This discovery shows a novel strategy to enhance the strength retention at high temperature of metallic nanolaminates through dynamic strain ageing of one the phases.

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