Evolution of Structure and Properties of Micro-Nano Structure 2507 Duplex Stainless Steel Prepared by Aluminothermic Reduction

In this work, a large ingot of micro-nano structure 2507 duplex stainless steel was prepared in a single step using the aluminothermic reaction method. Chromium having different excess fractions were added to reaction powders to make up for evaporation loss, and the results show that the composition and structure of 2507 duplex stainless steel with a chromium excess ratio of 70% are satisfactory. The volume fraction of nanocrystalline in as-cast alloy was 41% and the average grain size was 34 nm. Additionally, the anticipated steels were rolled roughly with deformation of 40% at 1000 degrees C and followed by fine rolling with deformation of 30, 50 and 70%, separately, at 800 degrees C. Then, the effects of rolling deformation and precipitation on mechanical properties were studied in detail. Compared with the as-cast alloy, there was no phase transformation in the alloys with deformation of 30 and 50%, and they were still composed of gamma and alpha phases, whereas the sigma phase appeared in the alloy with deformation of 70%. When the deformation was 50%, the rolled alloy achieved the best performance, and the tensile strength, yield strength, and elongation were 912 MPa, 523 MPa, and 24.3%, respectively.