The aim of this master thesis was to examine possibilities and limits for hybrid cast and wire arc additive manufactured applications on the example of a gearbox housing. To gather knowledge about the state of research an extensive literature research was done, that covers the main topics aluminium alloys in additive manufacturing, wire and arc additive manufacturing, process parameters, modification and defects and hybrid production processes. For the practical part of this thesis the feasibility of WAAM (Wire Arc Additive Manufacturing) added parts on a casted aluminium component was researched from a material science perspective. For that a parameter research and a comparison of two distinct parameter sets was conducted in order to find the best performing. With this knowledge hybrid material was produced and tested on its mechanical properties. Regarding the literature research on aluminium alloys in additive manufacturing, the main additive processes were presented that are used for aluminium, as well as their known benefits and drawbacks. The WAAM process and its different processing methods will be introduced and compared to similar additive processes based on welding techniques. Further the microstructure, typical material properties and applied heat treatments are researched. Already existing hybrid processes and a direct comparison of mechanical properties of additive to cast parts will be discussed. In the experimental part fundamental trends on the grain size, the maximum pore diameter and the width were researched. On that basis, two additive parameter sets were tested regarding achievable mechanical properties and microstructure. A beneficial strategy for additive material production could be determined and was used for the hybrid production. Hybrid material with an AlSi7Mg wire on a substrate with the same chemical composition was manufactured and tested. The joint between both materials shows no bondage flaws or any lack of fusion, but numerous clustered pores at the joint could be detected. The heat-affected zone in the cast was found to be the weakest part of the hybrid sample with a significant drop in tensile and fatigue strength. Serious concerns about the damage in the heat-affected zone and critical pore development are expressed. Whereas the overall porosity and the unquantified distortion were valued as minor concerns. Usage for commercial purposes is believed to be not possible at this stage, however utilisation in the components development process may already have advantages. Further research is strongly recommended.