## 1 Introduction
The phase segregation created in this way contributes to a reduction in the strength properties of the weld in the heat-affected zones. The degree of segregation and thus the susceptibility to hot cracking is decisively influenced by the difference in the amount of solid fraction in the weld pool and the zone of partial melting during solidification [40]. [PERSON] and [PERSON] [41], based on temperature-solid phase quantity diagrams, studied welded joints of cast Al-Si aluminium alloy components with Al-Mg and Al-Si additive material. They confirmed that hot cracking in cast alloys, as in heat-treatable alloys, depends on the course of the bond crystallisation and the zone of partial melting (the difference in the amount of solid phase). One of the most effective methods for preventing hot cracking is to achieve a change in structure from dendritic to fine-grained equiaxial during weld crystallisation. This can be achieved by adding certain alloying elements. As stated by [PERSON] et al. [42], vanadium, introduced into pure aluminium, promoted a change from a peritectic to an equiaxial alloy crystallisation mode. The resulting Al\({}_{10}\)V separations provided an effective barrier to grain growth. In another paper, [PERSON] et al. [43] showed that aluminium alloys containing zirconium in their composition were also characterised by a fine-grained structure with Al\({}_{3}\)Zr strengthening separations. [PERSON] [44] noted that zirconium not only affects the mode of crystallisation, but also reduces grain growth during the recrystallisation of AlMg alloys. [PERSON] [45] and [PERSON] [46] reported an extremely beneficial effect from scandium on the mechanical properties of aluminium alloys by strengthening them with Al\({}_{3}\)Sc precipitates. The effect of precipitation strengthening can be enhanced by the simultaneous addition of both zirconium and scandium to the aluminium alloy [47]. [PERSON]. [48] presented the possibility of introducing scandium and caesium simultaneously into alloys. The introduction of caesium made it possible to reduce the proportion of scandium and lower the manufacturing cost while maintaining the fine-grained structure of the aluminium alloy. Another element that strongly affects the joint structure of composite materials is the high electric arc energy, which can lead to the disintegration of the ceramic reinforcement. and the formation of undesirable brittle reaction products at the reinforcement-metal matrix interface. For this reason, the welding process parameters such as shielding gas output, current intensity or welding speed, and in particular the way in which the filler material formed from the mixture of the filler metal and the metal matrix crystallises and the strengthening precipitates formed in the process, are extremely important for the mechanical properties of the welded joint. Tests described in the literature to join cast aluminium alloy-based composites by TIG using the filling material AlMg (ER5356) or Al-Si (ER4347), which are used to join unreinforced aluminium alloys, were characterised by a number of welding discontinuities. Given the positive effects of alloying elements such as zirconium and scandium on the mechanical properties of aluminium alloys through precipitation strengthening, it seems reasonable to attempt to modify the commercial filling material with a suitable alloying element composition.