## 3 Results and Discussion
### Impact of ECAP Processing Factors  
#### 3.2.1 Microstructure Evolution  
EBSD was used to look into the microstructure of grains and the textural associated crystallography of both of the ECAP specimens and AA counterparts of Mg in pure form. The inverse pole figure (IPF) orientation map relevant to the extrusion direction (ED) for the AA billets is displayed in Figure 2. A microstructural dominance of roughly equiaxed coarse grains was observed, with a few outliers that were abnormally big and a few regions of exceedingly fine grains. Even further, substructures were visible, notably within the extremely immense grains. The grains varied greatly, from 1.14 \(\upmu\)m to 34 \(\upmu\)m, with 6.34 \(\upmu\)m being the mean. Information on grain size for ECAP specimens and their AA counterparts is depicted in Table 2. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Grain Size (\(\upmu\)m)**} & \multirow{2}{*}{**AA**} & \multicolumn{6}{c}{\(\boldsymbol{\Phi=90^{\circ}}\)} & \multicolumn{6}{c}{\(\boldsymbol{\Phi=120^{\circ}}\)} \\ \cline{3-11}  & & **1P** & **2A** & **2 Bc** & **2C** & **4 Bc** & **1P** & **2A** & **2 Bc** & **2C** & **4 Bc** \\ \hline Minimum & 1.1 & 0.64 & 0.56 & 0.5 & 0.68 & 0.21 & 1.1 & 0.68 & 0.5 & 0.5 & 0.81 \\ Maximum & 34 & 25.45 & 22.62 & 9.29 & 11.05 & 7.14 & 24.82 & 24.79 & 22.73 & 16.91 & 16.91 \\ Mean grain size & 6.34 & 1.96 & 1.69 & 1.49 & 1.57 & 0.88 & 2.62 & 1.75 & 1.89 & 1.94 & 1.89 \\ Standard deviation & 5.8 & 1.5 & 0.97 & 0.95 & 0.67 & 0.73 & 2.45 & 1.44 & 1.85 & 1.64 & 1.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of AA and ECAPed billets obtained grain sizes produced by utilizing two distinct die angles (\(\up\)) and various passes. Figure 1: Correlation chart of ECAP responses (H, \(\up\), \(\up\), and Gr) against their counterpart input parameters (N, \(\up\), and Rt). Figure 3 displays the IPF orientation maps in relation to the ED or the ECAPed billets using both the 90\({}^{\circ}\)-die and 120\({}^{\circ}\)-die. These maps were created for Mg billets processed through 1P and four passes of route Bc (4 Bc). The microstructure of pure Mg that was ECAP-processed for 1P was seen to show bimodality, with recently created fine and significantly deformed big grains, as shown in Figure 3a. A significant density of high-angle grain boundaries (HAGBs), also described as split into ultrafine grains, was discovered in regions of the Mg billets where a strain post-1P had led to the formation of dynamic recrystallization at local areas [50]. Since the AA microstructure is not homogeneous, the applied strain of 1P will have varying effects on the various microstructural properties. Hence, in some regions, this strain will be sufficient to initiate dynamic recrystallization and yield fine grains, whereas in other regions, it will not be sufficient. The bimodal microstructure produced following 1P, with grain sizes varying from 0.64 um to 25.45 um and averaging 1.96 um, was consistent with such a condition. The EBSD orientation maps showed that 1P caused a decrease in the mean of grain size, from 6.3 um for the BM to 1.96 um (Table 2). Moreover, the HAGBs between 15 and 80 degrees appeared to be more randomly distributed. As the misorientation angle approached 90 degrees, a weakening of the twin boundaries became apparent as well. The literature also revealed consistent results in regards to microstructural evolution. Following 1P ECAP processing at room temperature, [PERSON] and [PERSON] [45] noticed various grain sizes, with certain grains larger than the rest, with a size exceeding 50 um and a mean of 4.15 um. They claimed that the pure Mg microstructural obtained form was highly heterogeneous as a result of this observation. Different samples of pure Mg were ECAP-processed with 120\({}^{\circ}\) over a comparable number of passes to examine the impact of angle changing on the resulting microstructure and texture.