Effect of Nb on microstructure and corrosion resistance of Fe-Mn-Al-C low density steel
In order to explore the influence of Nb addition on the microstructure and corrosion resistance of Fe-28Mn-10A1-C low density steel and make clear its mechanism,the microstructure and precipitation characteristics with dif-ferent Nb content(0,0.3％,0.5％)were investigated by means of OM,SEM and TEM.The effect of Nb content on the corrosion resistance of Fe-28Mn-10Al-C alloy in 3.5％NaCl solution was investigated by electrochemical po-larization test and immersion corrosion.The microstructure of the test steel and the element distribution after corro-sion were observed and analyzed.The results show that the second phase of fcc-NbC is precipitated along the aus-tenite grain boundary after Nb is adding.As the Nb content increases from 0 to 0.5％,the austenite grain size de-creases from 39.49 μm to 13.67 μm,and the corrosion current density decreases from 6.17× 10-6 A/cm2 to 6.31 X 10-7 A/cm2.In addition,within the 72 hours corrosion period,the corrosion weight loss of the test steel decreases from 5.750 mg/mm2 to 4.625 mg/mm2.The results confirm that the austenite grain size is refined in the Nb-contai-ning alloys,and the surface stability of test steel during electrochemical polarization process is enhanced,which indi-cates that the electrochemical corrosion rate is also reduced with the increase of Nb content,and the corrosion resist-ance of test steel is further improved.The oxide film is formed on the surface of test steel after immersion corrosion.Al oxides mainly gather at the interface between oxide film and metal(O/M).Compared with the Nb-free test steel,the gather of Al oxides at the O/M interface is more obvious with Nb added.This indicates that the addition of Nb can promote the formation of Al oxide film on the surface of Fe-28Mn-10Al-C low density steel and reduce the corro-sion rate of the alloy.The data and conclusions obtained by experimental research can provide theoretical and re-search basis for further improving the corrosion resistance of Fe-Mn-Al-C low density steel.
Fe-Mn-Al-C steelNbmicrostructureprecipitation phasecorrosion resistanceoxide film
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