A great deal of stabilized retained austenite can be obtained by means of austempering immediately after intercritical annealing in the low-carbon plain steel sheets which only contain alloying elements of silicon and manganese. Transformation from retained austenite to martensite may be induced by strain at a temperature ranging from 50 ℃ to 400 ℃ during tension testing. Transformation-induced plasticity (TRIP) may occur. Alloying of silicon improves the stability of retained austenite. Mechanical properties of the present TRIP steels containing manganese increase with increasing silicon amount when the amount of silicon is less than two percent. A great deal of stabilized austenite can be obtained by means of austempering immediately after intercritical annealing in the low-carbon plain steel sheets which only contain alloying elements of silicon and manganese. Transformation from retained austenite to martensite may be induced by strain at a temperature Alloying of silicon improves the stability of retained austenite. ranging from 50 ℃ to 400 ℃ during tension testing. Transformation of induced plasticity (TRIP) may occur. is less than two percent