Grain boundary mediated plasticity: A blessing for the ductility of metallic thin films?. (15th August 2021)

• Record Type: Journal Article
• Authors: Liebig, Jan P.; Mačković, Mirza; Spiecker, Erdmann; Göken, Mathias; Merle, Benoit
• Is Part Of: Acta materialia. Volume 215(2021)
• Publication Date: 2021-08-15
• Subjects: Thin films -- Ductility -- Deformation mechanisms -- Transmission electron microscopy -- Nanomechanical testing; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2021.117079
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The limited ductility of metallic thin films (< 1%) poses a challenge to MEMS and flexible electronics applications. Here, we report on freestanding gold specimens with the remarkable ability to accommodate ≥10% plastic deformation while retaining a high strength. Using in situ nanomechanical testing in a transmission electron microscope, this exceptionally high ductility is traced back to the combination of an ultrathin thickness, a columnar microstructure and a (111) fiber texture. Under such conditions, the deformation is largely mediated by grain boundaries through grain boundary sliding and shear coupled grain boundary migration. Because these non-conventional mechanisms preserve the cross-sectional thickness of the specimens, necking is postponed and the samples can reach a high ductility. Since the mechanisms were evidenced at room temperature and under strain-rate conditions typical of most applications, the findings open up promising outlooks for developing ductile metallic films by microstructural engineering.