## 2 Materials and Methods  
### Materials and Experimental Methods  
The Mg employed currently measures 10 mm in radius and 500 mm long, and it is commercially pure (containing just 0.06% Al, 0.008% Ca, 0.005% Cr, 0.002% Cu, 0.015 Fe, 0.012% Mn, 0.005% Ni, and 0.06% Zn, and the balance is Mg). A precision cutting machine was employed, aiming at cutting the Mg billets into 60 mm long pieces for the ECAP samples. The specimens were annealed at 250 \({}^{\circ}\)C for 1 h prior to going through the ECAP. Single pass (1P), 2 passes (2P), and 4 passes (4P) of ECAP were employed to process the billets, along with a variety of routes (A, Bc, and C). A temperature of 225 degrees Celsius and a ram velocity of 0.05 mm per second were employed to carry out the ECAP process. After each pass, the die's interior surfaces were lubricated with a graphite-based substance to lessen frictional force across the specimens obtained from ECAP and the utilized die. The exterior angle (\(\Psi\)) of the split ECAP die employed was 20 degrees. Both of the adopted ECAP dies featured different inner channel angles (\(\phi\)) of 90\({}^{\circ}\) and 120\({}^{\circ}\). Scanning electron microscopy (SEM) was adopted to investigate the microstructural development of commercially available pure Mg billets. Furthermore, EBSD was applied to determine its structural progression and crystallographic texture both prior to and following the ECAP process. Both the AA and the ECAP billets were employed for the analysis of the microstructure, with cross-sections trimmed longitudinally (LS) in a given plane parallel to the orientation of the press (flow plane) and perpendicular to the die entrance channel), where the axes of the reference system coincide with the extrusion ECAP direction \"Y\" (ED), the normal direction \"Z\" (ND), and the transversal direction \"X\" (TD), as displayed in [27]. A conductive epoxy was employed for the cold mounting of the sample. Wheels revolving at a rate of 150 revolutions per minute were used to perform the grinding and polishing. The sample was cleaned with water in every grinding stage and then ground with 600, 800, 1000, and 1200-grit silicon carbide sandpaper. Diamond suspensions with a particle size of 3 and 1 \(\upmu\)m and a yellow DP-lubricant were employed in the initial polishing phase, while a colloidal silica suspension with a particle size of 0.05 \(\upmu\)m was employed for the last polishing phase, which lasted until an external surface without scratches was reached, which was detected with the use of an optical microscope. As a lubricant, water that had gone through the distillation process was employed. Following every phase of polishing, ultrasonic waves were employed to properly clean the sample using ethanol for 10 min; consequently, a drying process using a blow-dryer was performed. The sample was polished, then an etching in a hydrochloric acid and nitric acid mixture was performed (12 mL HCl + 8 mL HNO\({}_{3}\) + 100 mL ethanol) for a couple of seconds before being rinsed in ethanol. The etching spots or oxide coatings were removed from the sample's surface through ion milling for 30 min at 2 kev ion beam energy, 0.425 s\({}^{-1}\) sample rotating velocity, and an 85\({}^{\circ}\) sample inclination angle, where the sample surface was inclined at 5\({}^{\circ}\) comparative to the ion beam axis. At 15 kV, 1.5 nA average current, and a 70\({}^{\circ}\) inclination angle, an SU-70 SEM was employed to obtain EBSD observations on the upper surface of the ED plane. With a resolution of 100 nm, crystallographic data were acquired with the help of the HKL Channel5 Flanneco program. After gathering crystallographic data, a post-processing HKL Channel 5 program was employed to create an inverse pole figure (IPF) map. Testing for microhardness employing Vicker's method was carried out on the specimens prior to and following ECAP processing, beginning at the edges of the billets and working inward.