Community: 3D Characterization of Materials - High Energy Diffraction Methods Community
| Dataset | Description | Owner | Updated |
|---|---|---|---|
| Quantification of Cyclic Twinning-Detwinning Behavior During Low-Cycle Fatigue of Pure Magnesium Using High Energy X-Ray Defraction | The dataset contains the data supplement for: A.D. Murphy-Leonard, D.C. Pagan, A. Beaudoin, M.P. Miller, J.E. Allison, Quantification of cyclic twinning-detwinning behavior during low-cycle fatigue of pure magnesium using high energy X-ray diffraction. International Journal of Fatigue, 125 (2019), 314-323. https://doi.org/10.1016/j.ijfatigue.2019.04.011 The cyclic twinning and detwinning behavior of extruded Mg was investigated using in-situ high energy X-ray diffraction (HEXD) under fully-reversed low cycle fatigue conditions. Measurements were conducted at three levels of applied strain. The initial texture was such that the c-axis in most grains was perpendicular to the loading direction, an orientation in which extension twinning is favored during compressive loading. At strain amplitudes greater than 0.5%, tension-compression asymmetry was observed during cyclic loading and related to cyclic twinning and detwinning. The twinning and detwinning behavior were characterized by monitoring the evolution of X-ray diffraction peaks associated with the basal {0 0 0 2} planes throughout selected cycle. At cyclic strains greater than 0.5%, in-situ HEXD results show that twinning occurs during the compression portion of the cycle and, at early stages of fatigue, most twins are detwinned under reversed loading during the tensile portion of the cycle. It was also observed that as the number of fatigue cycles increases the twin volume fraction increases. After 100–200 fatigue cycles, the detwinning process was observed to be incomplete and a significant fraction of residual twins remained throughout an entire cycle. Using electron back scatter diffraction imaging on the surface of interrupted fatigue tests, twinning and detwinning behavior was investigated and the presence of persistent twins, including residual twins, was observed. At a lower applied strain (0.4%), twinning and tension-compression yield asymmetries associated with twinning were not observed. | Aeriel Murphy | 2 days ago |
| Characterization of cyclic twin evolution in a Mg-Nd alloy using high energy X-ray diffraction microscopy | Grain-scale twinning and detwinning in extruded Mg-2.4wt.%Nd was characterized using combined far-field and near-field High Energy X-Ray Diffraction Microscopy (HEDM) during fully reversed tension-compression cyclic straining. Nucleation of {101 ̅2} twins were identified by tracking the appearance or disappearance of {0002} diffraction peaks for all possible twin variants of each grain in the unloaded state. The evolution of twin volume fraction was measured by combining a near-field HEDM reconstructed 3D grain morphology and far-field HEDM spot integrated intensity during cyclic loading. The mechanical response and twin activity in the near-field HEDM reconstructed volume were simulated using a crystal plasticity finite element model with an advanced twinning-detwinning algorithm to characterize the impact of binary Nd alloying on critical resolved shear stresses for the operative slip modes and extension twinning. Twinning is observed during loading parallel to the extrusion axis in both tension and compression due to the weak rotated basal extrusion texture, with a higher total twin volume fraction and number of active variants observed during tensile loading. Twin activity is detected predominantly in large grains, and grains nominally oriented favorably for extension twinning and unfavorably for prismatic slip. Twin growth is observed to lead to elastic strain shielding in the parent lattice during continued macroscopic deformation, and elastic strain accommodated by twin growth is preferentially shifted to pyramidal II <c+a> slip systems during reversed displacement. | Duncan Greeley | 3 years ago |
| The dynamics of recrystallized grains during static recrystallization in a hot-compressed Mg-3.2Zn-0.1Ca wt.% alloy using in-situ far field high-energy diffraction microscopy | The poor formability of rolled magnesium (Mg) alloy sheet remains a barrier to its widespread commercial use and is attributed to the strong basal texture that occurs in most mechanically processed Mg alloys. Recent attempts to successfully weaken the texture have been made using Mg-Zn-Ca alloys in combination with post-deformation annealing. The motivation for this work is to understand the evolution of the mesoscale processes that occur during annealing (specifically, static recrystallization) and lead to this texture weakening. Toward this goal, more than 1,200 recrystallized grains were studied during in-situ annealing in an 80% hot-compressed Mg-3.2Zn-0.1Ca wt.% (ZX30) alloy using far-field high-energy diffraction (ff-HEDM). The relative volume, crystallographic orientation, and position of each recrystallized grain emerging within a 1×1×0.1 mm3 volume were tracked throughout static recrystallization. These measurements were used to quantitatively measure the nucleation and growth statistics associated with recrystallized grains as a function of annealing time. The measurements reflected a highly heterogeneous process with individual grain dynamics varying wildly from the average, and they also point to relations between relative grain volume and growth rate (or more accurately, the rate of change of relative grain volume) with a peak average rate occurring early in recrystallization (at 22% recrystallized). We also explore whether a recrystallized grain's current state can be used to predict its future growth behaviors with implications for Monte Carlo simulations. Finally, we investigate whether recrystallized grains with specific orientations have preferential nucleation and/or growth, and we find that grains with a weak basal texture have a pronounced nucleation advantage that increases with annealing time, while other grain orientations have a slight growth advantage that diminishes with annealing time. | Ashley Bucsek | 5 months ago |
| Characterization of recrystallized grains during static recrystallization of hot-compressed Mg-Zn-Ca alloys using in-situ far-field high-energy diffraction microscopy | Although rolled magnesium (Mg) alloys generally suffer from strong crystallographic textures and poor formability, adding Ca and Zn to magnesium sheet can result in a desirably weak recrystallization texture and improved formability. In this study, we explore the effect of Zn content on the static recrystallization of three 80% hot-compressed alloys, Mg-0.5Zn-0.1Ca wt.% (ZX050), Mg-1Zn-0.1Ca wt.% (ZX10) and Mg-3.2Zn-0.1Ca wt.% (ZX30), using far-field high-energy diffraction microscopy (ff-HEDM). Individual recrystallized grains are tracked and their 3D centroid, relative volume, and grain-averaged crystallographic orientation are measured during in-situ annealing. These measurements are used to compare the kinetics and texture evolution of recrystallized grains in ZX alloys as a function of Zn content. Fully recrystallized microstructures are observed for the ZX30 and the ZX10 alloys after annealing at 230ºC and 330ªC, respectively. In contrast, only a partially recrystallized microstructure for the ZX050 alloy is observed after >1 hour of annealing at 430ºC. The recrystallized grains also show slower growth rates for ZX050 as compared to ZX10 and ZX30. We also use the results to discuss the recrystallization grain textures, as well as the correlation between orientations and the nucleation and growth rates of recrystallized grains, both as a function of annealing time and Zn content. | Tracy Berman | 2 days ago |