Cold rolling effect on lightweight austenitic stainless-steel

In order to reduce the vehicles weight, in transportation and automotive sectors, designers are focusing on stronger materials with resisting cross section reduction or on lighter materials. Mn Al lightweight stainless-steels could represent an innovative response to both weight-reducing strategies due to high mechanical properties (Yield Strength even higher than 1000 MPa) and low density (15% lower than Hadfield steel and 16% lower than AISI 306L). Lightweight stainless-steels can have very different microstructure depending on the composition (ferritic, duplex or austenitic), but typically all of them undergo thermomechanical treatments to exploit precipitation hardening given mainly by κ-carbides formation. In this work, the effect of cold rolling on an austenitic lightweight stainless-steel alloy has been investigated, comparing the microstructure evolution and the mechanical properties, after the same thermal treatments, between the material in hot rolled and in cold rolled state (thickness reduction of 80%). The thermal treatments were defined in two ways: solubilization and ageing or directly ageing with two different temperatures and with different holding times (550°C and 600°C for 30min, 1h, 2.5h and 8h). The microstructure and the mechanical properties appear to be very different and with different evolution in the different cases studied and an interesting ongoing austenite transformation featured by the κ-carbide precipitation and the β-Mn formation has been observed.