The influence of copper addition on the formability of AISI 304 stainless steel

The formability of AISI 304 austenitic stainless steel can be enhanced when it is designed to transform to martensite under appropriate strain levels, gaining additional plasticity (transformation induced plasticity). In this work, the effects of a partial substitution of Ni by Cu on the formability of AISI 304 steel were analyzed in terms of microstructure changes during tensile straining. Conventional metallographic techniques aided by scanning probe microscopy were employed to identify and characterize the stress-induced martensitic phases. The results obtained are discussed in terms of the relationship between chemical composition and the stability of austenite, taking into account the stacking fault energy and the characteristics of stress-induced martensite in these steels. It has been observed that the partial substitution of Ni by Cu gave rise to an increase in the strain level required to induce martensitic transformation, resulting in higher maximum uniform elongation and better stretch formability.