The steel industry is forced by the automotive industry to produce inovative and marketable products for light-weight-constructions. This target can be achieved by designing high-strenght steels and out of this a possible material reduction. Dual-phase steels, which are part of these Advanced High Strenght Steels (AHSS) exhibit a complex microstructure. An optimization of their properties is only possible with a fundamental knowledge of the proceeding phase transformations. This diploma thesis deals with the phase transformation behaviour of seven selected alloy compositions. Particularly, the bainite formation pays a special attention because of its relevance in high-strenght steels. The selection of the alloying variants should reveal the influence of chromium and manganese on the transformation behaviour. The different variants were investigated by using optical and scanning electron microscope as well as dilatometer, MULTIPAS and atom probe. A combination of these techniques together with thermocalc-calculation, residual austenite measurements and mechanical values allow a meaningful characterisation of occurring mechanismen.