In situ indentation and high cycle tapping deformation responses in a nanolaminate crystalline/amorphous metal composite

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

卷:798

Article

Guo, Qianying^1,2  Gu, Yucong¹  Barr, Christopher M.³  Koenig, Thomas¹  Hattar, Khalid³  Li, Lin¹  Thompson, Gregory B.¹ 

[1] Univ Alabama, Dept Met & Mat Engn, Tuscaloosa, AL 35487 USA

[2] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA

[3] Sandia Natl Labs, Albuquerque, NM 87185 USA

关键词: Multilayer;    In situ TEM;    Automated crystal orientation mapping;    Crystalline/amorphous;    Indentation;    Cyclic loading;   

DOI  :  10.1016/j.msea.2020.140074

来源: Elsevier

【 摘 要 】

The incorporation of nanostructured and amorphous metals into modern applications is reliant on the under-standing of deformation and failure modes in constrained conditions. To study this, a 105 nm crystalline Cu/160 nm amorphous Cu45Zr55 (at.%) multilayer structure was fabricated with the two crystalline layers sputter deposited between the top-middle-bottom amorphous layers and prepared to electron transparency. The multilayer was then in situ indented either under a single load to a depth of similar to 100 nm (max load of similar to 100 mu N) or held at 20 mu N and then repeatedly indented with an additional 5 mu N up to 20,000 cycles in a transmission electron microscope to compare the deformation responses in the nanolaminate. For the single indentation test, the multilayer showed serrated load-displacement behavior upon initial indentation inductive of shear banding. At an indentation depth of 32 nm, the multilayer exhibited perfect plastic behavior and no strain hardening. Both indented and fatigue-indented films revealed diffraction contrast changes with deformation. Subsequent Automated Crystal Orientation Mapping (ACOM) measurements confirmed and quantified global texture changes in the crystalline layers with specifically identified grains revealing rotation. Using a finite element model, the in plane displacement vectors under the indent mapped conditions where ACOM determined grain rotation was observed, indicating the stress flow induced grain rotation. The single indented Cu layers also exhibited evidence of deformation induced grain growth, which was not evident in the fatigue-indented Cu based multilayer. Finally, the single indented multilayer retained a significant plastic crater in the upper most amorphous layer that directly contacted the indenter; a negligible crater impression in the same region was observed in the fatigued tested multilayer. These differences are explained by the different loading methods, applied load, and deformation mechanisms experienced in the multilayers.

【 授权许可】

Free