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Separation of Time Scales of Plastic Instabilities During Microscale Deformation of bcc Fe

Pozuelo, Marta ; Jiang, Katherine ; Marian, Jaime

Metallurgical and materials transactions. A, Physical metallurgy and materials science, 2021-09, Vol.52 (9), p.4275-4289 [Periódico revisado por pares]

New York: Springer US

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  • Título:
    Separation of Time Scales of Plastic Instabilities During Microscale Deformation of bcc Fe
  • Autor: Pozuelo, Marta ; Jiang, Katherine ; Marian, Jaime
  • Assuntos: Avalanches ; Characterization and Evaluation of Materials ; Chemistry and Materials Science ; Dynamic strain aging ; Frequency analysis ; High resolution electron microscopy ; Interstitials ; Materials Science ; Metallic Materials ; Microscopy ; Nanotechnology ; Numerical models ; Original Research Article ; Plastic deformation ; Plastic flow ; Plastic instability ; Precipitation hardening ; Room temperature ; Strain rate sensitivity ; Structural Materials ; Surfaces and Interfaces ; Thin Films
  • É parte de: Metallurgical and materials transactions. A, Physical metallurgy and materials science, 2021-09, Vol.52 (9), p.4275-4289
  • Descrição: During mechanical deformation of bcc Fe micropillars, a number of different plastic processes is activated, often leading to unstable plastic flow characterized by abrupt plastic discharges. While some of these instabilities are scale-free, such as dynamic strain aging (DSA), others such as plastic avalanches are strongly dependent on specimen dimensions, as well as temperature and strain rate. However, while these processes often have completely different underlying physical origins, they are difficult to separate and identify due to their co-occurring nature during plastic deformation. Understanding the onset and the evolution of these plastic mechanisms is thus important to separate their contributions during plastic flow and rationalize their dependence on specimen dimensions. In this work, we perform in-situ scanning electron microscopy microcompression tests of Fe micropillars at room-temperature and strain rates between 10 - 4 and 1.0 s −1 to study their plastic behavior and characterize the resulting deformation microstructures using high-resolution transmission electron microscopy. We develop a numerical model to extract the frequencies inherent to each plastic process and map them to the corresponding physical mechanisms. We find that dislocation avalanches occur on average with a frequency of 3 Hz in the low strain rate range (< 10 - 3 s −1 ) while solute-driven instabilities that result in a negative strain rate sensitivity occur with frequencies around 10 Hz. By contrast, at the highest strains rates (> 10 - 1 s –1 ) the two physical mechanisms become overlap in time with one another with frequencies around 100 Hz. Our frequency analysis agrees well with a DSA behavior controlled by interstitials impurities such as C, N and O and their interaction with dislocations.
  • Editor: New York: Springer US
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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