## 1 Introduction  
Development of multi-material parts has gained relevance during recent years due to the possibilities of adapting the mechanical properties of each material to the specific in-service requirements of the component. Thus, by combining different materials, it is possible to achieve a weight reduction and improve stiffness and strength among other properties; formability can also be improved thanks to the combination of properties. Because of this, the industrial technologies for advanced joining and assembly processes of multi-material have been identified as a critical research and development area of the European Union (EU) Horizon 2020 work program 2018-2020 [1]. In the aerospace industry, the reduction of the weight in the components is a key factor to increase the payload in aircrafts and satellites, saving fuel and reducing the environmental impact. For these reasons, the use of composite materials, such as thermoplastic or thermosetting resins combined with carbon fiber is very well implemented. Currently, additive manufacturing is acquiring more and more importance to reduce tooling costs and manufacture parts with impossible shapes using conventional methods, among other advantages related to the sustainability [2] and design optimization [3]. Additive manufacturing techniques can also be an alternative to conventional processes when design specifications of obsolete parts are difficult to obtain due to a lack of information, such as component drawings or bill of materials, as explained by [PERSON] et al. [4]. The problem with these kinds of multi-material components is the limitation in their in-service behavior, as composite materials cannot be used for high temperature requirements. Although additive manufacturing techniques are experiencing very quick improvements, still have poorer surface finishing and lower mechanical properties than parts made by conventional methods due to the layer by layer structure [5], the dimensions of the components to be manufactured are also limited. Furthermore, in the manufacturing of multi-material components by additive manufacturing, other factors, such as materials compatibility, formation of brittle inter-metallic metallurgical structures, residual stresses, and microstructure thermal effects become decisive. The co-extrusion process is typically used to obtain multi-material cylinders to be used as billets to manufacture components with complex shapes. This is a complex thermo-mechanical process due to the combination of plastic deformation and diffusion in the interface of both materials because of the pressure and temperatures generated. There are several studies about the combination of Mg and Al alloys, such as the one by [PERSON] et al. [6], where the influence of the die angle and different combining techniques of Mg-core and Al-sleeve on the diffusion layer formation are investigated. Another example is the work by [PERSON] et al. [7], where a ZM21 magnesium alloy/CP aluminum was fabricated through direct hot co-extrusion with three different extrusion ratios and constant temperature and ram speed. [PERSON] et al. [8] also studied the co-extrusion of bimetallic Al-Mg billets into hollow profiles by means of experiments and Finite Element Method (FEM) simulation. [PERSON] et al. [9] analyzed the mechanical strength and fracture properties of hydrostatic coextruded Al-Mg compounds. Other studies regarding multi-material co-extrusion have been performed using Cu-Al, for example, [PERSON] et al. [10] studied the inter-diffusion improvement in the manufacturing of Cu-Al bimetallic tubes using severe plastic deformation methods. [PERSON] et al. [11] analyzed the strain-stress state in bimetallic rods composed by Cu-Al using two different extrusion ratios in conical die and in double reduction die. A study about the deformation behavior of an Al/Cu clad composite by the method of twist channel angular pressing (TCAP) was conducted by [PERSON] et al. [12]; whereas [PERSON] et al.