## 3 Results and Discussion
### Texture Evolution of Alloy during Annealing
#### 3.2.2 Annealing Temperature Effect
Figure 13 shows the ODFs of the two samples, and their volume fractions of textures are summarized in Table 5; although, after being solution-treated at 500 \({}^{\circ}\)C for 0.5 h, Sample 1 preserves its very strong Brass texture (35.0%), while Sample 2 exhibits no evidently strong texture, which it is probably due to the randomized grain orientations arising from rolling in alternate directions. Figure 12: EBSD-derived IPF images of 80% cold-rolled samples after different annealing treatments: (a) 330 \({}^{\circ}\)C/0.5 h; (b) 420 \({}^{\circ}\)C/0.5 h; (c) 470 \({}^{\circ}\)C/0.5 h; (d) cube-orientated grains extracted from (a); (e) cube-orientated grains extracted from (b); (f) cube-orientated grains extracted from (c). The OM images of the two samples are shown in Figure 14. In both samples, most grains are elongated along the RD, and there are few equiaxed recrystallized grains. The average sizes of grains in these two samples are 312.3 \(\pm\) 5.9 and 303.1 \(\pm\) 6.4 \(\upmu\)m respectively (these are relatively large, a fact attributed to the continuous grain growth during processing, and the inhibition of recrystallization, which restricts grain refinement). Table 6 lists the mechanical tensile properties of two samples. Compared with Sample 2, both the yield strength (\(\sigma_{0.2}\)) and tensile strength (\(\sigma_{\rm b}\)) of Sample 1 increase, especially in the RD direction along which \(\sigma_{0.2}\) of Sample 1 is 39 MPa (\(\sim\)14.6%) greater than that of Sample 2; the elongations (8) of Sample 1 are lower than those of Sample 2 in both RD and TD directions, but the decreases are less than 3.2%. In addition, the strength of Sample 1 in the RD direction is much greater than that in the TD direction. This is probably attributed  
Figure 14: OM images of two T3-tempered samples: (**a**) Sample 1; (**b**) Sample 2. Figure 13: ODFs on the rolling plane of two T3-tempered samples: (**a**) sample 1; (**b**) sample 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Cube (\%)** & **Goss (\%)** & **Brass (\%)** & **Copper (\%)** & **S (\%)** \\ \hline Sample 1 & 5.24 & 4.52 & 35.0 & 8.10 & 9.17 \\ Sample 2 & 8.64 & 6.51 & 4.56 & 4.09 & 2.35 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Volume fractions of textures, calculated based on the ODFs of two T3-tempered samples (with a measurement accuracy of 0.05%). to the mechanical anisotropy caused by the strong Brass texture of Sample 1. Unlike Sample 1, there are only small differences in the mechanical properties of Sample 2 in the RD and TD directions, as it possesses no evident texture. Figure 15 shows the FCGR vs. the applied \(\triangle\)K of Samples 1 and 2, and an industrial 2524-T3 alloy: both Samples 1 and 2 have a lower FCGR at the same applied \(\triangle\)K, especially at low \(\triangle\)K values. Among these three samples, Sample 2 has the lowest FCGR at \(\sim\)75% and \(\sim\)31% less than those of the industrial alloy and Sample 1, respectively, at \(\triangle\)K = 10 MPa m\({}^{1/2}\). From the inserted OM image, Samples 1 and 2 contain coarser grains than the industrial 2524-T3 alloy, and their crack paths are also more tortuous. Previous studies [29; 32] showed that the coarse-grained samples possessed higher resistance to fatigue-crack growth, since it on the one hand deflected cracks and therefore increased the length of the crack path, and on the other hand produced a more evident roughness-induced crack closure [32]. Thus, the lower FCGRs of Samples 1 and 2 could be due to the higher crack closure level and lower driving force of crack growth, caused by coarser grain sizes. It is recognized that during fatigue loading, there is a reverse plastic region [33] with radius \(r_{p}\) at the crack tip when the applied stress changes.