Second order twinning in austenitic steel

It is mechanical twinning which dominates the plastic deformation of austenitic steel at high degrees of cold work. The process involves the formation of second order twins (SOT), which are twins being formed within an already twinned section. In the present paper those SOT configurations are described in terms of disclinations. It is shown that the elastic energy of a deformation twin can drastically be lowered by SOT formation. Conditions of SOT formation are discussed in terms of local stress concentrations within the initial dislocation structure. SOT formation decreases the average twinning strain and increases the work hardening rate. It is concluded that SOT systems are important structure elements with respect to the mechanical properties of austenitic steel.