Effect of Cu addition on phase fraction, mechanical properties and corrosion properties of Fe–Cr–Mn–Al duplex stainless steel

In recent years, Cu has been regarded as an important element to improve the corrosion resistance of stainless steels. For duplex stainless steels, especially those obtained by cold rolling and annealing, at present, little is known about the role mechanism of Cu addition. Therefore, on the basis of a new type of Fe–Cr–Mn–Al duplex stainless steel designed by the author, the effects of Cu on phase fraction, mechanical properties and corrosion resistance were studied in detail through tensile tests, electron backscattering diffraction (EBSD), polarization curve test and laser scanning confocal microscopy. The results show that the addition of 0.5% Cu to Fe–Cr–Mn–Al system increases the volume fraction of austenite and its stability, greatly improving the strength and ductility of steels due to the TRIP effect occurring in a wider strain range. In addition, the addition of Cu increases the content of Cr in austenite, improving the pitting resistance of duplex stainless steels. After annealing at 860 °C, the Cu-added duplex stainless steel exhibits superior mechanical and corrosive properties, i.e. the yield strength, tensile strength, elongation and pitting potential are 520 MPa, 760 MPa, 42.5% and 260 mV, respectively. In view of obvious advantages in mechanical properties and corrosion resistance, the present developed Cu-added Fe–Cr–Mn–Al duplex stainless steel is expected to replace the conventional 304 stainless steel for some applications.