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Initial microstructures of 7075 aluminum alloy in (a) rolling-transverse (R-T) plane and (b) rolling-normal (R-N) plane
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Three-dimensional crystal plasticity finite element (CPFE) method is used to investigate the hot compressive deformation behaviors of 7075 aluminum alloy. Based on the grain morphology and crystallographic texture of 7075 aluminum alloy, the microstructure-based representative volume element (RVE) model was established by the pole figure inversion...
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... EBSD system coupled with a Zeiss ULTRA plus scanning electron microscope (SEM) was applied in order to obtain the grain morphology and crystallographic orientation of 7075 aluminum alloy. Since the grain size of 7075 aluminum alloy is relative large, the scan step is chosen to be 2 lm. The rolling-transverse (R-T) and rolling-normal (R-N) planes of specimens were scanned, and the experimental results are shown in Fig. 1. The grain size of 7075 aluminum alloy can be determined as 500 lm 9 250 lm 9 50 lm from the inverse pole figure ...
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... hot deformation, the severely deformed regions have high stored energy. The nucleation of recrystallized grain is thermally activated process, and the driving force of nucleation is provided by the energy stored during hot deformation. However, the stored energy generated during hot deformation is too low to drive the homogeneous nucleation. Therefore, recrystallization nucleation usually occurs in the regions with local heterogeneities (Ref 69). As shown in Fig. 10, strain localization appears at the triple junction of grains 1, 2, and 3. This region with high strain amplitude may be the potential nucleation site for recrystallized ...
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... on Strain Distribution Figure 9 shows the effects of grain orientation and misori- entation on the strain field of 7075 aluminum alloy at the deformation degree of 60% in the R-T plane. The grain boundaries are highlighted using black lines. It can be seen that the distribution of strain is inhomogeneous due to different grain orientations. The strain concentration appears at some grain boundaries, resulting in a strain discontinuity at these grain boundaries. However, there is strain continuity across some other grain boundaries. As Raabe figured out (Ref 67), the crystal kinematics significantly affects the strain heteroge- neity between the neighbour grains. The grains with large strains are kinematically soft while the kinematically hard grains have small strains. During hot deformation, the strain path follows soft grains and avoids hard grains. However, the effects of the grain boundary misorientation on the strain distribution are not obvious in the R-T plane since the loading axial is perpendicular to the R-T plane. Figure 10(a) shows the strain distribution of 7075 aluminum alloy at the deformation degree of 60% in the R-N plane. The inhomogeneous strain field can also be found. From Fig. 10(a), a narrow area with relatively large strain value is marked with a quadrangle. Figure 10(b-d) shows the evolution of strain field in the quadrangle with the increase of deformation degree. In the R-N plane, the evolution of the strain field at the grain boundary junction can be easily observed in Fig. 10(b-d). At the deformation degree of 47%, a small area (the red area shown in Fig. 10b) with relatively large strain value appears at the grain boundary junction. As the deformation proceeds, this small area becomes larger and grows from the grain boundary to the grain interior. When the deformation degree is increased to 60%, the strain field with relatively large strain value expands from one grain to the adjacent grains. At the beginning of the hot deformation, the deformation incompatibility appears at the junction of the grain boundaries, resulting in the strain concentration. With the increase of the deformation degree, the strain concentration expands to the grain interior. In general, strain localization at triple junctions is more obvious than that at straight grain boundaries. Similar results from CP simula- tions were reported by Raabe et al. (Ref 67). It was found that the triple junctions might be the nucleation sites for strain localization, and the grain boundary misorientation affects the strain heterogeneity. From Fig. 10(d), it can be seen that the strain field cannot go across the grain boundary between grains 1 and 2, while the strain field can expand from grain 1 to grain 3. The occurrence of this phenomenon is possibly induced by the grain boundary misorientation. The grain boundary angle between grains 1 and 2 is relatively high (36.02°), while that between grains 1 and 3 is a low-angle grain boundary (5.83°). It can be concluded that the strain field can go across the low- angle grain boundaries, while high-angle grain boundaries act as barriers in the R-N plane. Similar simulation results were observed by Sachtleber et al. (Ref 68), who found that the maximum strain appears at high-angle grain boundaries while the effects of low-angle grain boundaries on strain distribution are less ...
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... on Strain Distribution Figure 9 shows the effects of grain orientation and misori- entation on the strain field of 7075 aluminum alloy at the deformation degree of 60% in the R-T plane. The grain boundaries are highlighted using black lines. It can be seen that the distribution of strain is inhomogeneous due to different grain orientations. The strain concentration appears at some grain boundaries, resulting in a strain discontinuity at these grain boundaries. However, there is strain continuity across some other grain boundaries. As Raabe figured out (Ref 67), the crystal kinematics significantly affects the strain heteroge- neity between the neighbour grains. The grains with large strains are kinematically soft while the kinematically hard grains have small strains. During hot deformation, the strain path follows soft grains and avoids hard grains. However, the effects of the grain boundary misorientation on the strain distribution are not obvious in the R-T plane since the loading axial is perpendicular to the R-T plane. Figure 10(a) shows the strain distribution of 7075 aluminum alloy at the deformation degree of 60% in the R-N plane. The inhomogeneous strain field can also be found. From Fig. 10(a), a narrow area with relatively large strain value is marked with a quadrangle. Figure 10(b-d) shows the evolution of strain field in the quadrangle with the increase of deformation degree. In the R-N plane, the evolution of the strain field at the grain boundary junction can be easily observed in Fig. 10(b-d). At the deformation degree of 47%, a small area (the red area shown in Fig. 10b) with relatively large strain value appears at the grain boundary junction. As the deformation proceeds, this small area becomes larger and grows from the grain boundary to the grain interior. When the deformation degree is increased to 60%, the strain field with relatively large strain value expands from one grain to the adjacent grains. At the beginning of the hot deformation, the deformation incompatibility appears at the junction of the grain boundaries, resulting in the strain concentration. With the increase of the deformation degree, the strain concentration expands to the grain interior. In general, strain localization at triple junctions is more obvious than that at straight grain boundaries. Similar results from CP simula- tions were reported by Raabe et al. (Ref 67). It was found that the triple junctions might be the nucleation sites for strain localization, and the grain boundary misorientation affects the strain heterogeneity. From Fig. 10(d), it can be seen that the strain field cannot go across the grain boundary between grains 1 and 2, while the strain field can expand from grain 1 to grain 3. The occurrence of this phenomenon is possibly induced by the grain boundary misorientation. The grain boundary angle between grains 1 and 2 is relatively high (36.02°), while that between grains 1 and 3 is a low-angle grain boundary (5.83°). It can be concluded that the strain field can go across the low- angle grain boundaries, while high-angle grain boundaries act as barriers in the R-N plane. Similar simulation results were observed by Sachtleber et al. (Ref 68), who found that the maximum strain appears at high-angle grain boundaries while the effects of low-angle grain boundaries on strain distribution are less ...
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... on Strain Distribution Figure 9 shows the effects of grain orientation and misori- entation on the strain field of 7075 aluminum alloy at the deformation degree of 60% in the R-T plane. The grain boundaries are highlighted using black lines. It can be seen that the distribution of strain is inhomogeneous due to different grain orientations. The strain concentration appears at some grain boundaries, resulting in a strain discontinuity at these grain boundaries. However, there is strain continuity across some other grain boundaries. As Raabe figured out (Ref 67), the crystal kinematics significantly affects the strain heteroge- neity between the neighbour grains. The grains with large strains are kinematically soft while the kinematically hard grains have small strains. During hot deformation, the strain path follows soft grains and avoids hard grains. However, the effects of the grain boundary misorientation on the strain distribution are not obvious in the R-T plane since the loading axial is perpendicular to the R-T plane. Figure 10(a) shows the strain distribution of 7075 aluminum alloy at the deformation degree of 60% in the R-N plane. The inhomogeneous strain field can also be found. From Fig. 10(a), a narrow area with relatively large strain value is marked with a quadrangle. Figure 10(b-d) shows the evolution of strain field in the quadrangle with the increase of deformation degree. In the R-N plane, the evolution of the strain field at the grain boundary junction can be easily observed in Fig. 10(b-d). At the deformation degree of 47%, a small area (the red area shown in Fig. 10b) with relatively large strain value appears at the grain boundary junction. As the deformation proceeds, this small area becomes larger and grows from the grain boundary to the grain interior. When the deformation degree is increased to 60%, the strain field with relatively large strain value expands from one grain to the adjacent grains. At the beginning of the hot deformation, the deformation incompatibility appears at the junction of the grain boundaries, resulting in the strain concentration. With the increase of the deformation degree, the strain concentration expands to the grain interior. In general, strain localization at triple junctions is more obvious than that at straight grain boundaries. Similar results from CP simula- tions were reported by Raabe et al. (Ref 67). It was found that the triple junctions might be the nucleation sites for strain localization, and the grain boundary misorientation affects the strain heterogeneity. From Fig. 10(d), it can be seen that the strain field cannot go across the grain boundary between grains 1 and 2, while the strain field can expand from grain 1 to grain 3. The occurrence of this phenomenon is possibly induced by the grain boundary misorientation. The grain boundary angle between grains 1 and 2 is relatively high (36.02°), while that between grains 1 and 3 is a low-angle grain boundary (5.83°). It can be concluded that the strain field can go across the low- angle grain boundaries, while high-angle grain boundaries act as barriers in the R-N plane. Similar simulation results were observed by Sachtleber et al. (Ref 68), who found that the maximum strain appears at high-angle grain boundaries while the effects of low-angle grain boundaries on strain distribution are less ...
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... on Strain Distribution Figure 9 shows the effects of grain orientation and misori- entation on the strain field of 7075 aluminum alloy at the deformation degree of 60% in the R-T plane. The grain boundaries are highlighted using black lines. It can be seen that the distribution of strain is inhomogeneous due to different grain orientations. The strain concentration appears at some grain boundaries, resulting in a strain discontinuity at these grain boundaries. However, there is strain continuity across some other grain boundaries. As Raabe figured out (Ref 67), the crystal kinematics significantly affects the strain heteroge- neity between the neighbour grains. The grains with large strains are kinematically soft while the kinematically hard grains have small strains. During hot deformation, the strain path follows soft grains and avoids hard grains. However, the effects of the grain boundary misorientation on the strain distribution are not obvious in the R-T plane since the loading axial is perpendicular to the R-T plane. Figure 10(a) shows the strain distribution of 7075 aluminum alloy at the deformation degree of 60% in the R-N plane. The inhomogeneous strain field can also be found. From Fig. 10(a), a narrow area with relatively large strain value is marked with a quadrangle. Figure 10(b-d) shows the evolution of strain field in the quadrangle with the increase of deformation degree. In the R-N plane, the evolution of the strain field at the grain boundary junction can be easily observed in Fig. 10(b-d). At the deformation degree of 47%, a small area (the red area shown in Fig. 10b) with relatively large strain value appears at the grain boundary junction. As the deformation proceeds, this small area becomes larger and grows from the grain boundary to the grain interior. When the deformation degree is increased to 60%, the strain field with relatively large strain value expands from one grain to the adjacent grains. At the beginning of the hot deformation, the deformation incompatibility appears at the junction of the grain boundaries, resulting in the strain concentration. With the increase of the deformation degree, the strain concentration expands to the grain interior. In general, strain localization at triple junctions is more obvious than that at straight grain boundaries. Similar results from CP simula- tions were reported by Raabe et al. (Ref 67). It was found that the triple junctions might be the nucleation sites for strain localization, and the grain boundary misorientation affects the strain heterogeneity. From Fig. 10(d), it can be seen that the strain field cannot go across the grain boundary between grains 1 and 2, while the strain field can expand from grain 1 to grain 3. The occurrence of this phenomenon is possibly induced by the grain boundary misorientation. The grain boundary angle between grains 1 and 2 is relatively high (36.02°), while that between grains 1 and 3 is a low-angle grain boundary (5.83°). It can be concluded that the strain field can go across the low- angle grain boundaries, while high-angle grain boundaries act as barriers in the R-N plane. Similar simulation results were observed by Sachtleber et al. (Ref 68), who found that the maximum strain appears at high-angle grain boundaries while the effects of low-angle grain boundaries on strain distribution are less ...
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... on Strain Distribution Figure 9 shows the effects of grain orientation and misori- entation on the strain field of 7075 aluminum alloy at the deformation degree of 60% in the R-T plane. The grain boundaries are highlighted using black lines. It can be seen that the distribution of strain is inhomogeneous due to different grain orientations. The strain concentration appears at some grain boundaries, resulting in a strain discontinuity at these grain boundaries. However, there is strain continuity across some other grain boundaries. As Raabe figured out (Ref 67), the crystal kinematics significantly affects the strain heteroge- neity between the neighbour grains. The grains with large strains are kinematically soft while the kinematically hard grains have small strains. During hot deformation, the strain path follows soft grains and avoids hard grains. However, the effects of the grain boundary misorientation on the strain distribution are not obvious in the R-T plane since the loading axial is perpendicular to the R-T plane. Figure 10(a) shows the strain distribution of 7075 aluminum alloy at the deformation degree of 60% in the R-N plane. The inhomogeneous strain field can also be found. From Fig. 10(a), a narrow area with relatively large strain value is marked with a quadrangle. Figure 10(b-d) shows the evolution of strain field in the quadrangle with the increase of deformation degree. In the R-N plane, the evolution of the strain field at the grain boundary junction can be easily observed in Fig. 10(b-d). At the deformation degree of 47%, a small area (the red area shown in Fig. 10b) with relatively large strain value appears at the grain boundary junction. As the deformation proceeds, this small area becomes larger and grows from the grain boundary to the grain interior. When the deformation degree is increased to 60%, the strain field with relatively large strain value expands from one grain to the adjacent grains. At the beginning of the hot deformation, the deformation incompatibility appears at the junction of the grain boundaries, resulting in the strain concentration. With the increase of the deformation degree, the strain concentration expands to the grain interior. In general, strain localization at triple junctions is more obvious than that at straight grain boundaries. Similar results from CP simula- tions were reported by Raabe et al. (Ref 67). It was found that the triple junctions might be the nucleation sites for strain localization, and the grain boundary misorientation affects the strain heterogeneity. From Fig. 10(d), it can be seen that the strain field cannot go across the grain boundary between grains 1 and 2, while the strain field can expand from grain 1 to grain 3. The occurrence of this phenomenon is possibly induced by the grain boundary misorientation. The grain boundary angle between grains 1 and 2 is relatively high (36.02°), while that between grains 1 and 3 is a low-angle grain boundary (5.83°). It can be concluded that the strain field can go across the low- angle grain boundaries, while high-angle grain boundaries act as barriers in the R-N plane. Similar simulation results were observed by Sachtleber et al. (Ref 68), who found that the maximum strain appears at high-angle grain boundaries while the effects of low-angle grain boundaries on strain distribution are less ...
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... on Strain Distribution Figure 9 shows the effects of grain orientation and misori- entation on the strain field of 7075 aluminum alloy at the deformation degree of 60% in the R-T plane. The grain boundaries are highlighted using black lines. It can be seen that the distribution of strain is inhomogeneous due to different grain orientations. The strain concentration appears at some grain boundaries, resulting in a strain discontinuity at these grain boundaries. However, there is strain continuity across some other grain boundaries. As Raabe figured out (Ref 67), the crystal kinematics significantly affects the strain heteroge- neity between the neighbour grains. The grains with large strains are kinematically soft while the kinematically hard grains have small strains. During hot deformation, the strain path follows soft grains and avoids hard grains. However, the effects of the grain boundary misorientation on the strain distribution are not obvious in the R-T plane since the loading axial is perpendicular to the R-T plane. Figure 10(a) shows the strain distribution of 7075 aluminum alloy at the deformation degree of 60% in the R-N plane. The inhomogeneous strain field can also be found. From Fig. 10(a), a narrow area with relatively large strain value is marked with a quadrangle. Figure 10(b-d) shows the evolution of strain field in the quadrangle with the increase of deformation degree. In the R-N plane, the evolution of the strain field at the grain boundary junction can be easily observed in Fig. 10(b-d). At the deformation degree of 47%, a small area (the red area shown in Fig. 10b) with relatively large strain value appears at the grain boundary junction. As the deformation proceeds, this small area becomes larger and grows from the grain boundary to the grain interior. When the deformation degree is increased to 60%, the strain field with relatively large strain value expands from one grain to the adjacent grains. At the beginning of the hot deformation, the deformation incompatibility appears at the junction of the grain boundaries, resulting in the strain concentration. With the increase of the deformation degree, the strain concentration expands to the grain interior. In general, strain localization at triple junctions is more obvious than that at straight grain boundaries. Similar results from CP simula- tions were reported by Raabe et al. (Ref 67). It was found that the triple junctions might be the nucleation sites for strain localization, and the grain boundary misorientation affects the strain heterogeneity. From Fig. 10(d), it can be seen that the strain field cannot go across the grain boundary between grains 1 and 2, while the strain field can expand from grain 1 to grain 3. The occurrence of this phenomenon is possibly induced by the grain boundary misorientation. The grain boundary angle between grains 1 and 2 is relatively high (36.02°), while that between grains 1 and 3 is a low-angle grain boundary (5.83°). It can be concluded that the strain field can go across the low- angle grain boundaries, while high-angle grain boundaries act as barriers in the R-N plane. Similar simulation results were observed by Sachtleber et al. (Ref 68), who found that the maximum strain appears at high-angle grain boundaries while the effects of low-angle grain boundaries on strain distribution are less ...
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... the texture tends to be stable, Fig. 11 shows only the 111 h i pole figures of grains 1, 2, and 3 after the compressive compression. It can be found that the pole figures of grains 1 and 3 are almost the same, and different from that of grain 2. It reveals that the grain boundary between grains 1 and 2 is still a high-angle grain boundary, while that between grains 1 and 3 is a low-angle grain boundary. The initial orientation of each element in one grain is the same, and the texture shown in pole figure is concentrated. As can be seen from Fig. 11, the texture is divergent after the deformation, which indicates that the deformation heterogeneity occurs in every grain (shown in Fig. 10). Zhao et al. (Ref 70) also found that the strain heterogeneity is significantly affected by the microtexture through experiments and 3D CP simulations. This is due to the separation of in-grain kinematics and grain interaction, as discussed by Raabe et al. (Ref ...
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... the texture tends to be stable, Fig. 11 shows only the 111 h i pole figures of grains 1, 2, and 3 after the compressive compression. It can be found that the pole figures of grains 1 and 3 are almost the same, and different from that of grain 2. It reveals that the grain boundary between grains 1 and 2 is still a high-angle grain boundary, while that between grains 1 and 3 is a low-angle grain boundary. The initial orientation of each element in one grain is the same, and the texture shown in pole figure is concentrated. As can be seen from Fig. 11, the texture is divergent after the deformation, which indicates that the deformation heterogeneity occurs in every grain (shown in Fig. 10). Zhao et al. (Ref 70) also found that the strain heterogeneity is significantly affected by the microtexture through experiments and 3D CP simulations. This is due to the separation of in-grain kinematics and grain interaction, as discussed by Raabe et al. (Ref ...
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... the texture tends to be stable, Fig. 11 shows only the 111 h i pole figures of grains 1, 2, and 3 after the compressive compression. It can be found that the pole figures of grains 1 and 3 are almost the same, and different from that of grain 2. It reveals that the grain boundary between grains 1 and 2 is still a high-angle grain boundary, while that between grains 1 and 3 is a low-angle grain boundary. The initial orientation of each element in one grain is the same, and the texture shown in pole figure is concentrated. As can be seen from Fig. 11, the texture is divergent after the deformation, which indicates that the deformation heterogeneity occurs in every grain (shown in Fig. 10). Zhao et al. (Ref 70) also found that the strain heterogeneity is significantly affected by the microtexture through experiments and 3D CP simulations. This is due to the separation of in-grain kinematics and grain interaction, as discussed by Raabe et al. (Ref ...
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... M 1 and M 2 are the orientation matrices for the initial and current orientations, respectively. The misorientation DH can be computed from the misorientation matrix A mis , and DH is formulated by Eq 11. There are 24 crystallographically equivalent misorientations considering the symmetry of the FCC crystal. The minimum of all the misorientations is adopted as the final misorientation for each element. Figure 12 shows the misorientation distribution of 7075 aluminum alloy after the hot deformation. The value of misorientation can be used to represent the rotation degree of each crystal. From Fig. 12, it can be found that the distribution of misorientation is inhomogeneous and the maximum misori- entation angle is 52.76°. The maximum misorientation appears at the edges of the RVE model, and most of the misorientations are less than 30°. The relatively homogeneous distribution of misorientation within the grain is observed, and misorientation continuity or discontinuity at the grain boundaries can be found. Also, the effects of grain boundary on the misorientation distribution are obvious in the R-N plane. As shown in Fig. 12(b), the misorientation of the grain boundary between grains 4 and 5 is 6.26°, while that between grains 5 and 6 is 55.68°. It can also be concluded that the misorientation continuity is present across the low-angle grain boundary, while the misorientation discontinuity appears at the high-angle grain boundary. Therefore, it can be concluded that the grain rotation incompatibility can occur at the high-angle grain boundary, and the low-angle grain boundary has little effect on the misorientation distribution during the hot-compressive ...
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... M 1 and M 2 are the orientation matrices for the initial and current orientations, respectively. The misorientation DH can be computed from the misorientation matrix A mis , and DH is formulated by Eq 11. There are 24 crystallographically equivalent misorientations considering the symmetry of the FCC crystal. The minimum of all the misorientations is adopted as the final misorientation for each element. Figure 12 shows the misorientation distribution of 7075 aluminum alloy after the hot deformation. The value of misorientation can be used to represent the rotation degree of each crystal. From Fig. 12, it can be found that the distribution of misorientation is inhomogeneous and the maximum misori- entation angle is 52.76°. The maximum misorientation appears at the edges of the RVE model, and most of the misorientations are less than 30°. The relatively homogeneous distribution of misorientation within the grain is observed, and misorientation continuity or discontinuity at the grain boundaries can be found. Also, the effects of grain boundary on the misorientation distribution are obvious in the R-N plane. As shown in Fig. 12(b), the misorientation of the grain boundary between grains 4 and 5 is 6.26°, while that between grains 5 and 6 is 55.68°. It can also be concluded that the misorientation continuity is present across the low-angle grain boundary, while the misorientation discontinuity appears at the high-angle grain boundary. Therefore, it can be concluded that the grain rotation incompatibility can occur at the high-angle grain boundary, and the low-angle grain boundary has little effect on the misorientation distribution during the hot-compressive ...
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... M 1 and M 2 are the orientation matrices for the initial and current orientations, respectively. The misorientation DH can be computed from the misorientation matrix A mis , and DH is formulated by Eq 11. There are 24 crystallographically equivalent misorientations considering the symmetry of the FCC crystal. The minimum of all the misorientations is adopted as the final misorientation for each element. Figure 12 shows the misorientation distribution of 7075 aluminum alloy after the hot deformation. The value of misorientation can be used to represent the rotation degree of each crystal. From Fig. 12, it can be found that the distribution of misorientation is inhomogeneous and the maximum misori- entation angle is 52.76°. The maximum misorientation appears at the edges of the RVE model, and most of the misorientations are less than 30°. The relatively homogeneous distribution of misorientation within the grain is observed, and misorientation continuity or discontinuity at the grain boundaries can be found. Also, the effects of grain boundary on the misorientation distribution are obvious in the R-N plane. As shown in Fig. 12(b), the misorientation of the grain boundary between grains 4 and 5 is 6.26°, while that between grains 5 and 6 is 55.68°. It can also be concluded that the misorientation continuity is present across the low-angle grain boundary, while the misorientation discontinuity appears at the high-angle grain boundary. Therefore, it can be concluded that the grain rotation incompatibility can occur at the high-angle grain boundary, and the low-angle grain boundary has little effect on the misorientation distribution during the hot-compressive ...
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The present study addresses the multi-scale computational modeling of a lightweight
Aluminum-Lithium (Al-Li) 2070 alloy. The Al-Li alloys display significant anisotropy
in material properties because of their strong crystallographic texture. To understand
the relationships between processing, microstructural textures at different material
points and tailored material properties, a multi-scale simulation is performed by
controlling the texture evolution during deformation. To achieve the multi-scale
framework, a crystal plasticity model based on a one-point probability descriptor,
Orientation Distribution Function (ODF), is implemented to study the texture
evolution. Next, a two-way coupled multi-scale model is developed, where the
deformation gradient at the macro-scale integration points is passed to the micro-
scale ODF model and the homogenized stress tensor at the micro-scale is passed back
to the macro-scale model. A gradient-based optimization scheme which incorporates
the multi-scale continuum sensitivity method is utilized to calibrate the slip system
parameters of the alloy using the available experimental data. Next, the multi-scale
simulations are performed for compression and tension using the calibrated crystal
plasticity model, and the texture data is compared to the experiments. With the
presented multi-scale modeling scheme, we achieve the location-specific texture
predictions for a new generation Al-Li alloy for different deformation processes.
... Moreover, the initial orientations of individual grains are obtained by discretizing the orientation distribution function (ODF) of EBSD data. Further details of orientation discretization and assignment can be found in [27]. The set of constitutive parameters used in the present study is shown in Table 1, where the elastic constants of NiTi SMA are obtained from the literature [9]. ...
Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA) are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM). Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD) density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.
... Accounting for the physical background of material, the theory of dislocation density, thermodynamics, and crystal plasticity are successively introduced, and some physically based constitutive models were reported. [18][19][20] The detailed background of dislocation density-based model is introduced in Sec. II. ...
Generally, the obvious work hardening, dynamic recrystallization (DRX), and dynamic recovery behaviors can be found during hot deformation of Ni-based superalloys. In the present study, the classical dislocation density theory is improved by introducing a new dislocation annihilation item to represent the influences of DRX on dislocation density evolution for a Ni-based superalloy. Based on the improved dislocation density theory, the peak strain corresponding to peak stress and the critical strain for initiating DRX can be determined, and the improved DRX kinetics equations and grain size evolution models are developed. The physical framework and algorithmic idea of the improved dislocation density theory are clarified. Moreover, the deformed microstructures are characterized and quantitatively correlated to validate the improved dislocation density theory. It is found that the improved dislocation density-based models can precisely characterize hot deformation and DRX behaviors for the studied superalloy under the tested conditions.
