Quantification and simulation of slip transfer across grain boundaries in near-cube oriented aluminum and meso-scale elastic strain heterogeneity in titanium
Thomas R. Bieler1,2, Reza Alizadeh2, Saara Haouala2, Zebang Zheng3, Philip Eisenlohr1, Javier Seguardo2, Javier Llorca2, Fionn Dunne3, Darren C. Pagan4, Armand Beaudoin4
1 Michigan State University, East Lansing, MI USA
2 IMDEA Materiales, Madrid, Spain
3 Imperial College, London, UK
4 CHESS, Ithaca, NY USA
Heterogeneous deformation in metallic polycrystals arises from several factors, including anisotropy in elastic properties and plastic slip. The ability to accurately simulate heterogeneous deformation requires physically based models of slip that includes grain boundary properties, as grain boundaries are usually barriers to slip. As slip transfer across boundaries occurs in some boundaries, grain boundary properties have been installed in a dislocation density based crystal plasticity model to enable slip transfer, and used to examine idealized bicrystal tensile samples. This code will be used to simulate deformation of annealed pure aluminum foil multicrystal experiments, in order to examine thresholds for slip transfer. An analysis of slip transfer events indicates that for near-cube oriented grains, the threshold is higher than observed in hexagonal materials, and potential reasons for this will be discussed.
Secondly, as computational simulations of polycrystals normally assume a zero-stress initial condition, this assumption is questionable in non-cubic metals where the coefficient of thermal expansion (CTE) is anisotropic. To assess the effect of the anisotropic CTE on initial stress states, two pure titanium samples with different textures were examined using in-situ high energy x-ray diffraction microscopy to measure the evolution of the internal stresses in each grain during heating and cooling. These data show a significant change in expansion rates in the <a> and <c> directions at about 700 C. A simulation of this experiment shows good agreement with experimentally measured data, indicating that it is possible to start a simulation with a good estimate of the internal stress state arising from the anisotropic CTE.
This work was supported by grants from US DOE/BES and the Community of Madrid.
Prof. Thomas R. Bieler
Michigan State University
College of Engineering
428 S. Shaw Lane
East Lansing
MI, 48824, USA
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