Ductile-to-brittle transition in a Zeron (R) 100 SDSS in wrought and aged conditions

Duplex Stainless Steels (DSS) are ferritic-austenitic stainless steels that posses mechanical and corrosion resistance properties which are improved if compared to the other stainless steels grades. DSS retain a considerable impact fracture toughness even to low temperature and, if compared with ferritic stainless steels, the ductile-to-brittle transition is more gradual. Nevertheless, these steels are sensitive to secondary phases precipitation during isothermal heat treatments, even for very low ageing times, especially in the temperature range over 600 degrees C. In the present work, the ductile-to-brittle transition of a Zeron (R) 100 Super DSS was investigated considering two different microstructural conditions. The material was tested in wrought ("as-received") and aged (isothermally heat treated) states by means of Charpy-V impact tests, in a temperature range between 20 degrees C and -120 degrees C. The aim of the work is that of provide a good representation of the toughness behaviour in the transition region by means of a regression analysis of the experimental data and to point out the effect of the precipitation of a slight amount of secondary phases (< 0.5%) on the impact toughness response. The results show that the material retains a good impact toughness even at -100 degrees C, but a slight amount of secondary phases affects the toughness behaviour by lowering the absorbed energy by about 80 J at room temperature, and this difference in toughness can be considered almost constant for all the experimental temperature range. For all the tested specimens the lateral expansion was also evaluated in order to achieve a further parameter to characterise the plastic deformation in the transition region. (C) 2013 Elsevier B.V. All rights reserved.