High entropy alloys are a relatively young class of metallic materials and have gained increasing popularity in research within the last decade. The regime of high entropy alloys is vast and largely undiscovered, making it possible that there might be hidden materials with exceptional properties. In this master thesis a series of high entropy alloys, based on the equiatomic compositions of AlTiMnNbV and AlTiMoNbV, are tested on their ability to form a solid solution, their thermal stability and their microstructural evolution in response to heat treatments. The goal is to find an alloy which forms a single-phase solid solution and shows reasonable stability at higher temperatures.