Polycrystal Plasticity: Comparison Between Grain - Scale Observations of Deformation and Simulations

Abstract

The response of polycrystals to plastic deformation is studied at the level of variations within individual grains, and comparisons are made to theoretical calculations using crystal plasticity (CP). We provide a brief overview of CP and a review of the literature, which is dominated by surface observations. The motivating question asks how well CP represents the mesoscale behavior of large populations of dislocations (as carriers of plastic strain). The literature shows consistently that only moderate agreement is found between experiment and calculation. We supplement this with a current example of microstructure evolution in the interior of a copper sample subjected to tensile deformation. Nondestructive measurements of orientation fields were performed using the near-field highenergy X-ray diffraction microscopy (nf-HEDM) technique at the Advanced Photon Source (APS). Starting at highly ordered grains, a single two-dimensional slice of microstructure containing ∼150 grains was followed through multiple strain states, where it tracked lattice rotations and defect accumulation of up to 14% elongation. In accord with the literature, at the scale of individual grains, comparison of observations with CP models indicates reasonable qualitative agreement but significant variations between simulation and experiment are apparent. The conclusion is that in order to be able to quantify the effects of microstructure on the distributions of slip, orientation change, and damage accumulation, the empirically derived constitutive relations used in continuumscale simulations need to be improved. Equally important will be the development of large-scale simulations of polycrystals that directly model dislocations. 317Annu. Rev. Condens. Matter Phys. 2014.5:317-346. Downloaded from www.annualreviews.org by University of Texas -San Antonio on 08/26/14. For personal use only.

Shock induced damage in copper: A before and after, three-dimensional study

“…It is also observed that the dispersion of orientations within grains increases significantly after the shock, much as is observed in quasi-static loading measurements. 8 There are some differences in the microstructure local to the voided region relative to the unvoided regions of microstructure. A subregion of the ROI was used to evaluate these differences by first forming a Laplacian surface that enclosed all the voids, then expanding this surface isotropically by 100 lm.…”

“…[1][2][3] Recent advances in nondestructive characterization have allowed for some of the first direct comparisons between quasi-static models of plasticity in polycrystals [4][5][6][7] and experiment. [8][9][10] With the goal of linking to dynamic models, [11][12][13][14][15] we leverage these advances to study high strain-rate plasticity through shock loading of coarse-grained copper and discuss the first non-destructive characterization of dynamic damage nucleation in the bulk.…”

Deformation-induced orientation spread in individual bulk grains of an interstitial-free steel

“…Reconstruction from near-field data only has resulted in detailed space-filling grain maps, including spatial information about the orientation spread within individual grains [11,40]. The method is especially well-suited for direct comparison with finite-element-based crystal plasticity simulations, focusing on the local effects of grain interaction, e.g.…”

A rotational and axial motion system load frame insert for in situ high energy x-ray studies

“…For example, adoption of an integrated computational materials engineering (ICME) approach to design of structural components is dependent on such a capability. [1][2][3][4][5][6] Development of trusted microstructure-sensitive deformation models may provide improved predictions of materials behavior, e.g., strength and damage resistance, enabling structural materials to be used more effectively and efficiently. While development of mesoscale models has been a major thrust of the materials community for several decades, these models have lacked the necessary multi-scale experimental validation, thus precluding design engineers from adopting them due to unacceptable risk factors.…”

“…Looking forward, advanced materials characterization methods are positioned to play a critical role in the validation and future development of mesoscale models and the long term goal of transitioning such modeling tools to the design community. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] One particular suite of experimental techniques that promises to be extremely fruitful in this endeavor is known as high energy diffraction microscopy (HEDM) or three-dimensional x-ray diffraction (3DXRD). 6,[21][22][23] These techniques utilize high energy monochromatic synchrotron radiation and area a) Author to whom correspondence should be addressed.…”