## 2 Materials and Methods  
_Processing._ This research developed a processing route that involved the following steps:  
To begin, Cr pieces with sizes that ranged from 2 to 2.5 cm were carefully struck with a hammer to produce particles ranging in size from 0.5 mm to 1 mm. The Cr particles were then mechanically milled until they had an average particle size of 37.9 um, as shown in Figure 1b, which is a schematic representation of the ball mill where the ball milling process was carried out. The Al and Cr powder mixture was then mechanically milled for various periods of time to reduce the particle sizes of the metallic elements, achieve a uniform chemical blend of both Al and Cr elements, and promote Cr alloying into Al (see Figure 1b). The Al and Cr powder mixture was pressed in a cylindrical mold at room temperature using one uniaxial press, as shown in Figure 1c. Following that, the green compacts obtained from uniaxial pressing were sintered in an ultrahigh vacuum furnace, as shown in Figure 1d. The following sections detail the operating parameters involved in each stage developed throughout the powder metallurgical processing route established in this study. _Materials._ Elemental powders of Cr and Al (both with a purity of 99.9%) were mixed in a mortar to obtain the compositions of Al-5 Cr (wt.%) and Al-7.5 Cr (wt.%). _Ball milling of powder mixture._ In a hardened steel vial containing stainless steel balls, the powder mixture was placed. The process control agent (PCA) was analytical grade methyl alcohol, which was injected to the powder blend in a 0.003 mL/g ratio. Under an argon atmosphere, the metallic powder mixture was placed inside the reinforced steel vial and closed with a cover. The metallic powder blend was then mechanically milled in the specified mill at 400 RPM for various milling durations (in order to characterize the evolution of microstructure by X-ray diffraction technique) until a total process time of 20 h was reached. The mechanical milling process employed a balls-to-powder weight ratio of 10:1. Figure 1: The process route developed in this study incorporates the utilization of various processes such as: (**a**) crushing, together with (**b**) ball milling, (**c**) uniaxial pressing, and (**d**) sintering. Consolidation of previously ball-milled powders.During the pressing process, the previously ball-milled Al-Cr powder mixture was subjected to uniaxial pressing at room temperature, a pressure of 750 MPa was employed. In addition, the pressing time was fixed at 10 min (see compaction cycle in Figure 2a). Once the green compacts were obtained by the uniaxial pressing process, then the specimens produced under the specified conditions were subjected to sintering process. In this thermal processing, the specimens were heated from ambient temperature to 475 \({}^{\circ}\)C and retained there for 1 h. (see sintering cycle in Figure 2a). The sintering process was performed inside an ultra-high vacuum furnace displayed in Figure 2b. Microstructural characterization.The consolidated specimens were chemically etched with a Keller reagent with a composition (% vol.) of 10 mL H\({}_{2}\)O, 3 mL HCl, 2 mL HF and 5 mL HNO\({}_{3}\). A scanning electron microscope ((SEM) mark HITACHI model SU15 IO) was used to analyze the evolution of powder morphology, particle size changes, and the tendency of chemical homogeneity of the powder mixture during the ball milling process. An X-ray energy dispersive (EDS) analyzer coupled with SEM was also utilized to conduct precise chemical analyses and X-ray mappings on un-milled and processed materials. In addition, while the milling period had elapsed, scanning electron microscopy was used to evaluate the chemical composition and phase distribution. In the same way, the sintered specimens were analyzed by SEM including the techniques mentioned above.