Tensile properties of austempered ductile iron under thermomechanical treatment

A new processing method was investigated for improving the strength and elongation of austempered ductile iron (ADI) by grain refinement of parent austenite using thermomechanical treatment, The material was deformed at the austenitization temperature by single and multipass rolling before the austempering treatment. The effects of the amount of deformation. austenitization temperature, austempering temperatures, reaustenitization, and secondary deformation on the tensile properties were studied. The properties obtained using the method were compared with those of the ASTM standards. The effect of deformation on the graphite shape was also studied. Tensile strength/yield strength/elongation values were found to increase with increasing austenite deformation up to 40% and then to start decreasing. Tensile strength/yield strength and elongation values of 1700 MPa/1300 MPa5% and 1350 MPa/920 MPa/15% can be achieved with this method in the ranges of variables studied.