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Metal Crystals—II Directionality
Published in Alan Cottrell, An Introduction to Metallurgy, 2019
To show any preferred orientations or textures which may exist in a polycrystalline metal it is usual to use not a standard projection but a pole figure. In this the stereogram is aligned to the overall geometrical features of the specimen (e.g. basic circle parallel to the plane of a rolled metal sheet) and the numbers of grains in various ranges of orientation are then indicated in it by a series of contour lines or by density of shading. The experimental information is usually obtained from the relative intensities of x-ray reflections from the polycrystal at various angular settings. Fig. 18.4 shows an example, the distribution of [111] crystal axes in heavily rolled alpha-brass sheet. This corresponds approximately to a (110) [112] texture, i.e. with (110) planes parallel to the rolling plane and [112] directions parallel to the rolling direction.
Development of powder bed fusion – laser beam process for AISI 4140, 4340 and 8620 low-alloy steel
Published in Powder Metallurgy, 2023
William Hearn, Peter Harlin, Eduard Hryha
Results from EBSD are presented in Figure 11. Examination of the band contrast found that the boundaries of the deposited melt tracks had the lowest indexing, as these regions contained many fine grains as well as grain boundaries. Reconstruction of the parent austenite grains found that they were predominantly composed of small columnar grains, along with a few equiaxed grains. In terms of their orientation, they were somewhat aligned with the building direction, however a distinct crystallographic texture was not observed. Inverse pole figure mapping of martensite also revealed a lack of crystallographic texture. This was reinforced from the pole figure mapping, see Figure 12, where a relatively random orientation was observed for each low-alloy steel.
Effect of microstructure on fracture in age hardenable Al alloys
Published in Philosophical Magazine, 2020
Rama K. Sabat, Waqas Muhammad, Raja K. Mishra, Kaan Inal
The texture of the initial and bend samples in the form of (111) pole figure is shown in Figure 3. The as-received sample is dominated by the recrystallisation texture followed by the rolling texture S component. A lower fraction of Copper and Goss components are present in the initial material. A significant change in texture components is observed during bending. Hence, to identify the texture components, the orientation distribution function is calculated and is shown in Figure 4. The cube texture is rotated either towards rolling direction (RD) or normal direction (ND) after 120° bending. A significant rotation of copper texture along ϕ1 axis and small rotation of S texture component are noticed after 120° bending. As deformation proceeds, that is, with an increase in bend angle to 135°, the S texture component disappeared. The CubeRD component weakens further at a bend angle of 135°. The known deformation texture components, namely Cube, S, Cu, completely disappeared after bending the sample to 150°. The maximum texture intensity of the initial, 120° bend, 135° bend, and 150° bend samples are nearly 3.2 m.r.d (multiples of random distribution), 2.1, 2.9 and 2.6 m.r.d, respectively. The trend of texture intensity shows an alternative increase and decrease in texture strength of maximum intensity with an increase in bend angle. However, the maximum texture intensity of all the bend samples is lowered compared to the maximum texture intensity of the initial sample.
Many-beam dynamical scattering simulations for scanning and transmission electron microscopy modalities for 2D and 3D quasicrystals
Published in Philosophical Magazine, 2019
Saransh Singh, William C. Lenthe, Marc De Graef
Dictionary indexing was performed on a two phase sample containing the decagonal AlNiCo phase and an unknown intermetallic phase. Figure 5(a,b) shows the orientation similarity map and the confidence index maps as defined in the dictionary indexing approach [38,39]. Since the indexing was performed only with respect to the quasicrystal, these regions appear bright in both maps. An inverse pole figure map, typically used to represent orientations in polycrystalline microstructures, can also be constructed by assigning a unique colour to each point of the asymmetric unit of the stereographic projection. An example inverse pole figure map and the colour legend for the decagonal point group are shown in Figure 5(c, d); note that the colour is assigned based on the formalism described in [40]. The IPF map shows that the orientation of the quasicrystalline phase remains almost constant throughout the field of view, indicating a potential dendritic growth mode for the quasicrystalline phase. This is consistent with real-time 3D x-ray tomography analysis performed for the growth of this sample [34]. IPF colour legends for other 2D and 3D quasicrystal symmetries can be found in Appendix 1.