## 1 Introduction  
Al-Mg-based alloys are widely used in industry. However, modern technologies require the use of new/modified materials with improved physical and mechanical properties. For example, such materials with enhanced properties are metal-matrix composites [1; 2; 3; 4; 5]. Among those, the application area of composites based on Al-Mg can be found in the automotive, marine, aerospace and electronics industries. The use of such composites in electrovacuum devices--in particular, as cathode (electron emitter) materials in gas-discharge devices, plasma installations, ion sources, sputtering systems, etc.--can also be considered. Since the cathodes in such devices operate under gas discharge conditions, the cathode's material should have a low-value electron WF and a low sputtering rate. In this regard, studies of the WF and sputtering rate of Al-Mg composites are of practical interest. The production of MMCs typically involves a combination of two or more materials with different properties, which are then mixed and processed to create a uniform distribution of the dispersed phase in the metallic matrix. One of the most common methods for producing MMCs is through powder metallurgy, which involves mixing the powders of the matrix and dispersed materials, followed by compaction and sintering. Another method is liquid-metal infiltration, in which a porous preform made of the dispersed phase is infiltrated with molten metal to create the composite. One may also recall such methods as spray forming, squeeze or stir casting [6], accumulative roll bonding [7], explosive bonding [8], friction stir welding, powder technologies, etc. However, severe plastic deformation (SPD) has emerged as a promising method for the in situ manufacturing of MMCs with improved properties. SPD processes, such as high-pressure torsion (HPT), impose large strains on the material, leading to severe deformation and the mixing of the materials at the atomic level. HPT is a popular SPD process that involves subjecting a sample to a torsional shear under high pressure in a confined space, which leads to the plastic deformation and homogenization of the material. MMCs obtained via SPD processes have improved mechanical and physical properties compared with conventionally produced MMCs, making them a promising area of research and development [9; 10; 11]. HPT is characterized by the highest shear strains in a material without fractures [12]. This method has been used for the manufacturing of homogeneous composite structures in Al-Cu [9; 13; 14], Al-Ti [15; 16], Al-Mg [17; 18] and various other systems, even including as dissimilar a combination as Al-Nb [19]. The main advantage of the HPT process is the possibility of manufacturing composites without contamination and residual porosity in one step at room temperature. Several studies have investigated the fabrication and properties of Al-based MMCs produced with HPT. For instance, one study reports the creation of an aluminum-based composite material reinforced with SiC particles through HPT [20]. The material exhibited enhanced wear resistance and mechanical properties compared with the base alloy. Another study describes the fabrication of an MMC using HPT on Al and aluminum oxide powders [21]. The resulting material showed improved hardness and compressive strength compared with pure Al. The addition of nanoparticles to the matrix has also been investigated to improve the properties of MMCs produced with HPT. In one study, an Al-Mg alloy reinforced with TiB\({}_{2}\) nanoparticles was fabricated using HPT, and the results showed improved mechanical properties and wear resistance [22]. Similarly, Al-graphene oxide composites were fabricated with HPT, and the material exhibited enhanced strength and ductility compared with the base aluminum [23]. The use of different reinforcing particles, such as nano-SiC particles [24], carbon nanotubes [25], alumina particles [26] and TiC particles [27], has also been investigated to improve the properties of Al-based MMCs produced with HPT.