Dominating deformation mechanisms in ultrafine-grained chromium across length scales and temperatures. (November 2017)

• Record Type: Journal Article
• Authors: Fritz, R.; Wimler, D.; Leitner, A.; Maier-Kiener, V.; Kiener, D.
• Is Part Of: Acta materialia. Volume 140(2017)
• Page Start: 176
• Page End: 187
• Publication Date: 2017-11
• Subjects: Strain-rate sensitivity -- Ultrafine-grained materials -- Thermally activated processes -- Elevated temperature testing -- In-situ -- Scale-bridging experiments; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.08.043
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The microstructure influence on the thermally activated deformation behaviour of chromium is investigated for a more fundamental understanding of the deformation mechanisms contributing to plasticity in bcc metals. Therefore, scale-bridging experiments at variable temperatures and varying strain-rates are performed, encompassing macroscopic compression tests in direct correlation to local in-situ SEM micro-compression experiments on taper-free pillars and advanced nanoindentation testing. For the first time, it is demonstrated that, independent of stress state, sample volume and surface fraction, a distinct temperature-dependent transition of the dominating deformation mechanism occurs. While at low temperatures the lattice resistance dominates, exceeding a critical temperature the dislocation interaction with grain boundaries becomes the rate limiting step. Finally, based on the vastly different fractions of grain boundaries in the tested sample volumes, a comprehensive model on the deformation of bcc metals, in particular at small scales or for confined volumes is derived. Graphical abstract: Image 1