**Andrea Francesco Ciuffini 1,\*, Silvia Barella 1, Cosmo Di Cecca 1, Andrea Di Schino 2, Andrea Gruttadauria 1, Giuseppe Napoli <sup>2</sup> and Carlo Mapelli <sup>1</sup>**


Received: 17 January 2019; Accepted: 3 February 2019; Published: 6 February 2019

**Abstract:** Due to their unique combination of properties, Super Duplex Stainless Steels (SDSSs) are materials of choice in many industries. Their applications and markets are growing continuously, and without any doubt, there is a great potential for further volume increase. In recent years, intensive research has been performed on lean SDSSs improving mechanical properties exploiting the lack of nickel to generate metastable γ-austenite, resulting in transformation-induced plasticity (TRIP) effect. In the present work, a commercial F55-UNS S32760 SDSS have been studied coupling its microstructural features, especially secondary austenitic precipitates, and tensile properties, after different thermal treatments. First, the investigated specimens have been undergone to a thermal treatment solution, and then, to an annealing treatment with different holding times, in order to simulate the common hot-forming industrial practice. The results of microstructural investigations and mechanical testing highlight the occurrence of TRIP processes. This feature has been related to the Magee effect, concerning the secondary austenitic precipitates nucleated via martensitic-shear transformation.

**Keywords:** steel; austenite; mechanical characterization; martensitic transformations; phase transformation
