posted on 2012-11-13, 11:02authored byMinsheng Huang, Liguo Zhao, Jie Tong
Discrete dislocation dynamics (DDD) has been used to model the deformation of nickelbased
single crystal superalloys with a high volume fraction of precipitates at high temperature.
A representative volume cell (RVC), comprising of both the precipitate and the
matrix phase, was employed in the simulation where a periodic boundary condition was
applied. The dislocation Frank–Read sources were randomly assigned with an initial density
on the 12 octahedral slip systems in the matrix channel. Precipitate shearing by superdislocations
was modelled using a back force model, and the coherency stress was
considered by applying an initial internal stress field. Strain-controlled loading was applied
to the RVC in the [0 0 1] direction. In addition to dislocation structure and density evolution,
global stress–strain responses were also modelled considering the influence of precipitate
shearing, precipitate morphology, internal microstructure scale (channel width and
precipitate size) and coherency stress. A three-stage stress–strain response observed in
the experiments was modelled when precipitate shearing by superdislocations was considered.
The polarised dislocation structure deposited on the precipitate/matrix interface was
found to be the dominant strain hardening mechanism. Internal microstructure size, precipitate
shape and arrangement can significantly affect the deformation of the single crystal
superalloy by changing the constraint effect and dislocation mobility. The coherency
stress field has a negligible influence on the stress–strain response, at least for cuboidal
precipitates considered in the simulation. Preliminary work was also carried out to simulate
the cyclic deformation in a single crystal Ni-based superalloy using the DDD model,
although no cyclic hardening or softening was captured due to the lack of precipitate
shearing and dislocation cross slip for the applied strain considered.
History
School
Mechanical, Electrical and Manufacturing Engineering
Citation
HUANG, M., ZHAO, L. and TONG, J., 2012. Discrete dislocation dynamics modelling of mechanical deformation of nickel-based single crystal superalloys. International Journal of Plasticity, 28 (1), pp. 141-158.
This is the author’s version of a work that was accepted for publication in the journal, International Journal of Plasticity. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ijplas.2011.07.003