Effect of low aging temperature and the reversion of martensite on the mechanical behavior of a 2304 lean duplex stainless steel

The effect of aging temperature on martensite reversion and mechanical behavior of a 2304-lean duplex stainless steel (LDSS) was analyzed after cold rolling to 74% reduction and aging at 400–600 °C for 1800 s. Strain-induced martensite (SIM) formation results from cold rolling. After cold rolling, the results revealed a Nishiyama–Wasser (N–W) relationship between the ∝ '-martensite laths and the metastable austenite. Increasing the aging temperature led to a rise in the steel strength, resulting in very low ductility, but with high yield and tensile strength of the specimens. The SIM reversion started between 500 and 550 °C for 1800 s soaking time. At temperatures between 400 and 500 °C, substantial embrittlement occurred. Precipitation of the ∝ + ∝ ′ (spinodal decomposition) in solid solution in ferrite was not observed. Hence, it is not the cause of the steel embrittlement. The mechanisms involved in the increase of strength and embrittlement were the aging of the austenite phase due to the formation of a substructure with ultrafine or nano-deformation twins, stacking faults, and shear bands in a lamellar array, and possibly Suzuki effect mechanism occurrence.