High concentrations of silicon and/or aluminium are used to suppress carbide formation in low-alloyed transformation induced plasticity (TRIP) steels, but these high contents can cause several problems during processing. The influence of reduced aluminium contents on phase transformations, microstructure evolution and mechanical properties in four low-alloyed TRIP steels is investigated. To achieve the appropriate annealing parameters for completed recrystallisation and total cementite dissolution, annealing simulations were performed. The influence of the cooling rate after intercritical annealing on the transformation behavior of austenite to pro-eutectoid ferrite and detailed investigations of the bainite formation during isothermal holding were carried out by dilatometric investigations. These results are confirmed by thermodynamic calculations like the T0-concept. The interpretation of the phase transformation is supported by investigations of the microstructure via light and scanning electron microscopy and measurements of the content of retained austenite using a magnetic volumetric method. Additionally, the mechanical properties were measured after applying different isothermal holding temperature and times in laboratory annealing simulations. An applicable fact, the mechanical stability of the retained austenite against martensitic transformation, is enlightened by detailed analysis of the stress-strain behaviour of the tensile tests.