TY - JOUR
T1 - In situ TEM study of microplasticity and Bauschinger effect in nanocrystalline metals
AU - Rajagopalan, Jagannathan
AU - Rentenberger, Christian
AU - Peter Karnthaler, H.
AU - Dehm, Gerhard
AU - Saif, M. Taher A.
N1 - Funding Information:
This material is based upon work supported by the National Science Foundation under Award No. NSF ECS-0304243 and Award No. NSF CMMI-0728189. The gold and aluminum specimens were fabricated in the Micro-nano-mechanical Systems Cleanroom and Micro Nano Technology Laboratory at the University of Illinois at Urbana-Champaign. The in situ TEM experiments were performed at the University of Vienna, supported by the research focus “Materials Science – Functional Materials and Nanostructures”. We thank Prof. Hael Mughrabi (University of Erlangen) for valuable discussions.
PY - 2010/8
Y1 - 2010/8
N2 - In situ transmission electron microscopy straining experiments with concurrent macroscopic stress-strain measurements were performed to study the effect of microstructural heterogeneity on the deformation behavior of nanocrystalline metal films. In microstructurally heterogeneous gold films (mean grain size dm = 70 nm) comprising randomly oriented grains, dislocation activity is confined to relatively larger grains, with smaller grains deforming elastically, even at applied strains approaching 1.2%. This extended microplasticity leads to build-up of internal stresses, inducing a large Bauschinger effect during unloading. Microstructurally heterogeneous aluminum films (dm = 140 nm) also show similar behavior. In contrast, microstructurally homogeneous aluminum films comprising mainly two grain families, both favorably oriented for dislocation glide, show limited microplastic deformation and minimal Bauschinger effect despite having a comparable mean grain size (dm = 120 nm). A simple model is proposed to describe these observations. Overall, our results emphasize the need to consider both microstructural size and heterogeneity in modeling the mechanical behavior of nanocrystalline metals.
AB - In situ transmission electron microscopy straining experiments with concurrent macroscopic stress-strain measurements were performed to study the effect of microstructural heterogeneity on the deformation behavior of nanocrystalline metal films. In microstructurally heterogeneous gold films (mean grain size dm = 70 nm) comprising randomly oriented grains, dislocation activity is confined to relatively larger grains, with smaller grains deforming elastically, even at applied strains approaching 1.2%. This extended microplasticity leads to build-up of internal stresses, inducing a large Bauschinger effect during unloading. Microstructurally heterogeneous aluminum films (dm = 140 nm) also show similar behavior. In contrast, microstructurally homogeneous aluminum films comprising mainly two grain families, both favorably oriented for dislocation glide, show limited microplastic deformation and minimal Bauschinger effect despite having a comparable mean grain size (dm = 120 nm). A simple model is proposed to describe these observations. Overall, our results emphasize the need to consider both microstructural size and heterogeneity in modeling the mechanical behavior of nanocrystalline metals.
KW - Microstructural heterogeneity
KW - Nanocrystalline materials
KW - Plastic deformation
KW - Thin films
KW - Yield phenomena
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U2 - 10.1016/j.actamat.2010.05.013
DO - 10.1016/j.actamat.2010.05.013
M3 - Article
AN - SCOPUS:77953872399
SN - 1359-6454
VL - 58
SP - 4772
EP - 4782
JO - Acta Materialia
JF - Acta Materialia
IS - 14
ER -