A cold rolled and heat treated steel sheet having a composition containing the following elements, expressed in percent by weight: 0.15%≤carbon≤0.6%; 4%≤manganese≤20%; 5%≤aluminum≤15%; 0≤silicon≤2%; aluminum+silicon≥6.5%; and possibly one or more of the following elements: 0.01%≤niobium≤0.3%; 0.01%≤titanium≤0.2%; 0.01%≤vanadium≤0.6%; 0.01%≤copper≤2.0%; 0.01%≤nickel≤2.0%; cerium≤0.1%; boron≤0.01%; magnesium≤0.05%; zirconium≤0.05%; molybdenum≤2.0%; tantalum≤2.0%; tungsten≤2.0%; the remainder being composed of iron and unavoidable impurities caused by processing, wherein the microstructure of said steel sheet contains in area fraction, 10 to 50% of austenite, the reminder being regular ferrite and ordered ferrite of D03 structure. A manufacturing method and use of the steel sheet for making vehicle parts is also described.