TY - JOUR

T1 - Dominating deformation mechanisms in ultrafine-grained chromium across length scales and temperatures

AU - Fritz, Reinhard

AU - Wimler, David

AU - Leitner, Alexander

AU - Maier-Kiener, Verena

AU - Kiener, Daniel

PY - 2017/11/1

Y1 - 2017/11/1

N2 - 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.

AB - 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.

KW - Elevated temperature testing

KW - In-situ

KW - Scale-bridging experiments

KW - Strain-rate sensitivity

KW - Thermally activated processes

KW - Ultrafine-grained materials

UR - http://www.scopus.com/inward/record.url?scp=85028082947&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2017.08.043

DO - 10.1016/j.actamat.2017.08.043

M3 - Article

AN - SCOPUS:85028082947

VL - 140.2017

SP - 176

EP - 187

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - November

ER -