## 3 Results
### Microstructures
#### 3.2.4 Texture Evolution  
Figure 9 shows the ODFs for the PA, CR and CR-373K (1200 min) samples. The texture components and corresponding percentages are shown in Table 2. As shown in Figure 9 and Table 2, the rolling texture content of the PA samples was 15.17% and the random orientation accounted for a relatively large amount, which was 72.88%. In the CR sample, a typical \(\beta\)-fiber was formed from copper {112} <111> through S {123} <634> to brass {110} <112> [26]. Compared with those of the PA samples, the strength and percentage of the brass {110} <112>, S {123} <634> and copper {112} <111> textures in the CR samples increased significantly. The total rolling texture percentage was 59.16% and the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Alloy Sample** & **d/nm** & \(\epsilon\)**/\%** & \(\rho\)**/m\({}^{-2}\)** \\ \hline CR & 16 & 0.18 & \(1.4\times 10^{15}\) \\ \hline CR-373K (420 min) & 51 & 0.21 & \(5.0\times 10^{14}\) \\ \hline CR-373K (1200 min) & 71 & 0.23 & \(3.9\times 10^{14}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Microcrystalline sizes, microstrains and dislocation densities of the CR and CR-373K samples. Figure 8: XRD patterns of the Al-Cu-Mn alloy in the CR and CR-373K conditions. random orientation proportion decreased to 23.15%. In addition, the strength and percentage of the cube {001} <100> and Goss {110} <001> textures increased slightly. The subsequent aging did not change the texture type of the CR samples. As shown in Figure 9c, the percentage of the rolled texture was 61.49% and the percentage of the other textures was 21.91%. Based on the above analysis of the texture type and percentage content, the Taylor factor was calculated using the following formula \(M_{A}=\Sigma f_{i}M_{i}\)[27; 28] (where fi and Mi are the percentage content and Taylor factor of different textures, respectively). Table 2 lists the Taylor factor values for the three samples. The Taylor factor value of the CR-373K (1200 min) samples was almost the same as that of the CR samples at 3.15 and 3.14, respectively; both were higher than the 3.04 value of the PA samples. Figure 10 shows the SEM images for the fracture surfaces of the PA, CR and CR-AG373K (1200 min) samples. The PA sample exhibited a typical feature of ductile failure with large- and small-sized dimples over the entire fracture surface (Figure 10a,b). This indicated that the fracture mechanism of the PA samples was mainly a dimple-induced transgranular fracture. After fracture, smooth regions (white frame in Figure 10c) were detected on the CR sample in addition to the intergranular cracks and transgranular dimples. In addition, at higher magnifications, shallow shear dimples were also observed (yellow arrows in Figure 10d). Therefore, the fracture mechanism of the CR samples was also dominated by the dimple-induced transgranular fracture. As shown in Figure 10e,f, the fractographies of the CR-373K (1200 min) sample also consisted mainly of transgranular dimples. The above three samples were formed via ductile fracture mechanisms while the dimples in the CR and CR-373K (1200 min) samples were smaller than those in the PA samples due to their smaller grains. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Alloy Sample** & \begin{tabular}{c} **Cube** \\ **(2.45)** \\ \end{tabular} & \begin{tabular}{c} **Goss** \\ **(2.45)** \\ \end{tabular} & \begin{tabular}{c} **Brass** \\ **(3.17)** \\ \end{tabular} & \begin{tabular}{c} **S** \\ **(3.33)** \\ \end{tabular} & \begin{tabular}{c} **Copper** \\ **(3.7)** \\ \end{tabular} & \
\begin{tabular}{c} **Random** \\ **(3.07)** \\ \end{tabular} &
\begin{tabular}{c} **Rolling** \\ **Texture** \\ \end{tabular} & \(\mathbf{M_{A}}\) \\ \hline PA & 5.25 & 6.13 & 5.83 & 5.42 & 4.49 & 72.88 & 15.17 & 3.04 \\ \hline CR & 6.89 & 10.80 & 11.56 & 36.67 & 10.93 & 23.15 & 59.16 & 3.14 \\ \hline CR-373K (1200 min) & 6.50 & 10.10 & 15.19 & 33.77 & 12.53 & 21.91 & 61.49 & 3.15 \\ \hline \hline \end{tabular}
\end{table}