Effect of Alloying Element of Cu on Phase Proportion, 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 processes, no research report on the effect of adding Cu element has been found so far. Therefore, on the basis of Fe-Cr-Mn-Al new duplex stainless steel developed by the author earlier, this study adopts scanning electron microscope microscopic analysis, electron backscattering diffraction microscopic analysis, tensile properties test, polarization curve test and high-temperature laser confocal test by adding an appropriate amount of Cu element. The effects of Cu on the phase proportion, mechanical properties and corrosion resistance of duplex stainless steel were analyzed. The results show that the addition of 0.5%Cu to Fe-Cr-Mn-Al system increases the volume fraction of austenite, improves the stability of austenite, makes TRIP effect occur in a wider strain range, and obviously improves the strength and plasticity of experimental steel. In addition, the addition of Cu leads to the increase the content of Cr in austenite, which improves the pitting resistance of experimental steel. When annealed at 860°C, the yield strength, tensile strength, elongation and pitting potential of the experimental steel with Cu addition are 520MPa, 760MPa, 42.5% and 260mV, respectively. The comprehensive properties of the experimental steel with Cu addition are obviously higher than those without Cu addition. Compared with 304 stainless steel, the experimental steel added with Cu has obvious advantages in mechanical properties and corrosion resistance, so it is expected to replace 304 stainless steel in some applications.