Inter-relation between true stress at the onset of necking and true uniform strain in steels – A manifestation of onset to plastic instability

A linear relation is observed between the true stress at the onset of necking and true uniform strain in type 316L(N) austenitic steel and P91 ferritic steel over wide range of test conditions. The observed linear relation between the true stress at the onset of necking and true uniform strain has been rationalised in terms of the onset to plastic instability. The strain regime, over which the alloy deforms by stable plastic flow, is directly proportional to the tensile strength.