A method of production of a cold rolled and heat treated steel sheet has the following steps: providing a cold rolled steel sheet with a composition including 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%, a remainder being composed of iron and unavoidable impurities caused by processing; heating said cold rolled steel sheet up to a soaking temperature between 80° and 950° C. during less than 600 seconds, then cooling the sheet down to a temperature in a range of 600° C. to room temperature, reheating the steel sheet to a soaking temperature of 150° C. to 600° C. during 10 s to 250 h, then cooling the sheet.