## 3 Results and Discussion
### Texture Evolution of Alloy during Cold Rolling
#### 3.1.2 CSP Effects  
Figure 5 demonstrates the back-scattered electron (BSE) images of the as-hot-rolled 2524 alloy. There are many CSPs with a size ranging from 5 to 30 \(\upmu\)m arranged along the RD of the sample (Figure 5a). According to EDS analysis, these CSPs mainly include S(Al2 CuMg) (Figure 5b) and AlCuFeMn phases (Figure 5c), which are the main inclusions present in this alloy [8; 29]. To assess the effect of second-phase particles on the deformation characteristics of alloy, the RD-ND plane of the sample was polished on which some straight scratches were preserved deliberately so that the local deformation behavior of the region near CSPs can be determined by comparing the changes in the shape of these scratches before and after cold rolling. Figure 6 shows the SEM images of the RD-ND plane of the sample after 10% cold rolling. As shown in Figure 6a,b, deflections (\(\sim\)18\({}^{\circ}\)) and displacements of the scratches can frequently be observed as they cross the interface between the CSPs and alloy matrix. This indicates that significant deformation discontinuities are present in the local region near the CSPs, given the aforementioned discontinuity of deformation: this leads to significant stress concentration in the near-CSP region, causing crack initiation at the interface of the CSPs (Figure 6c) and the fracture thereof (Figure 6d). Figure 7 shows TEM images of the region near an AlCuFeMn-phase particle in the sample after 80% cold rolling. It indicates that a high density of dislocations evolves to form many cellular structures caused by the great deformation. Compared with Figure 7a,b, the sizes of the cellular structures are shown to be smaller in the matrix adjacent to the interface of the particle than those only \(\sim\)3 \(\upmu\)m from the interface. As the wall of this cellular structure comprises a high density of dislocations, it is believed that the smaller the cellular structure, the higher the dislocation density. According to the theory of plastic deformation [30], the relationship between dislocation density (\(\rho\)) and strain (\(\epsilon\)) of an alloy is given by:  
\[d_{\epsilon}=\frac{bg}{\beta}\cdot\frac{d\rho}{\rho^{\frac{1}{2}}} \tag{1}\]  
where \(b\) is the Burgers vector, and \(g\) and \(\beta\) represent constants. There is a more serious strain at the region closer to the CSPs, as it has a higher dislocation density. This is mainly because many dislocations are blocked and accumulated at the interface of CSPs during cold rolling. This phenomenon will undoubtedly aggravate the non-uniformity of deformation in certain areas. Figure 5: BSE images and EDS results of the as-hot-rolled sample: (**a**) macroscopic BSE image showing the CSPs arranged along RD; (**b**) BSE image and EDS result indicating ellipsoidal-shaped S(Al2 CuMg) phase; (**c**) BSE image and EDS result indicating the presence of an irregularly shaped AlCuFeMn phase. To reveal the effect of CSPs on the texture evolution of alloy during cold rolling, the hot-rolled alloy samples were pre-annealed at 495 \({}^{\circ}\)C for 2 h so that most CSPs were dissolved into the alloy matrix, and their volume fractions of textures after different deformations were compared with those without pre-annealing (Figure 2). Figure 8 shows the sections (\(\varphi\) = 0\({}^{\circ}\)) of ODFs of pre-annealed samples after different amounts of deformation (i.e., 10%, 40%, and 80%).