The effect of the substitution of aluminium by phosphorus on the microstructure and the mechanical properties of cold rolled C-Mn-Si-Al TRIP-aided steels was investigated for different continuous annealing cycles. The TRIP-aided steel composition with mass contents of 0.42% Si, 0.58% Al and 0.07% P resulted in a total elongation of 29% and a tensile strength of 728 MPa. Lower amounts of Si resulted in lower ductility. The investigated steels had a high n-value at low strains. The CMnSIAlP TRIP-aided steel had a high and constant n-value during the entire stress-strain curve. The volume fraction of retained austenite, measured by X-ray diffraction, was 10% for the CMnSiAlP grade. For TRIP-aided steels with lower Si and/or Al content the volume fraction of retained austenite was less than 6%.e
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