Characterization and modeling of the interplay between grain boundaries and heterogeneous plasticity in titanium
Final Report Abstract
A software toolbox (”STABiX”) and three GUIs (EBSD map, bicrystal and preCPFE ) were developed to analyze strain transfer across grain boundaries. The toolbox enables a reduction of possible sources of error in the analysis by visualization and a standardized workflow with automated data conversion. The slip systems for bcc, fcc and hcp structures and several slip transfer criterions are implemented to quantify the potential for slip transmission at GBs in SINGLE phase and two phase materials. By a combination of spherical indentation inside grains and close to GBs with EBSD mapping and indent topography measurement by AFM, grain boundary slip transmission was characterized using the toolbox in cp < α > Titanium and near < α > Ti-5Al-2.5Sn (wt%) (used as model materials with hexagonal lattice structure and limited ductility). Preliminary results suggest that slip transfer in < α > Titanium is mainly controlled by the geometrical alignment of adjacent slip systems (mainly basal and prismatic 1st order a slips) at the boundary. Due to the toolbox interfaced with a Python package, CPFE simulation input files were generated for single and bicrystal indentation testing, for MSC Marc/Mentat and Abaqus/CAE FEM softwares. Quantitative comparisons between AFM measured and simulated nanoindentations were carried out both for single crystal indentations and bicrystal indentations. In both cases the locations and shapes of pile-ups agree quite well between experimental and simulated pile-up topographies. Discrepancies between experimental and simulated single crystal topographies are explained by the reverse plasticity after large plastic deformation. Differences between bicrystal experiments and models are additionally attributed to the lack of a dislocation description in the current purely phenomenological hardening model. Quantitatively, the bicrystal simulations are less accurate due to the influences of different grain boundary than single crystal simulations. Low angle boundary indents are simulated most accurate in all bicrystal indentation simulations. A physical description of grain boundary resistance would be necessary to better evaluate interactions between dislocations and grain boundaries in the future, with potential other experiments (e.g.: 3D EBSD), which could provide additional information about the interactions between dislocations and grain boundaries and the stress state beneath the indent.
Publications
- Orientation informed nanoindentation of alphatitanium: Indentation pileup in hexagonal metals deforming by prismatic slip. Journal of Materials Research, 27(01):356–367, 2012
C. Zambaldi, Y. Yang, T. R. Bieler, and D. Raabe
(See online at https://doi.org/10.1557/jmr.2011.334) - Grain boundaries and interfaces in slip transfer. Current Opinion in Solid State and Materials Science, 18:212–226, 2014. ISSN 1359-0286
T. R. Bieler, P. Eisenlohr, C. Zhang, H. Phukan, and M. A. Crimp
(See online at https://doi.org/10.1016/j.cossms.2014.05.003) - A Matlab toolbox to analyze slip transfer through grain boundaries. Proceedings of ICOTOM17, IOP Conference Series: Materials Science and Engineering, 82, 2015
C. Mercier, D. Zambaldi and T. R. Bieler
(See online at https://doi.org/10.1088/1757-899X/82/1/012090) - Quantifying deformation process near grain boundaries in α titanium using nanoindentation and crystal plasticity modeling. International Journal of Plasticity, Volume 86, November 2016, Pages 170-186
Su Yang, C. Zambaldi, D. Mercier, P. Eisenlohr, M. A. Crimp, and T. R. Bieler
(See online at https://doi.org/10.1016/j.ijplas.2016.08.007)
