Rolling tuning microstructure and tensile properties of nano/microcrystalline 304 stainless steel

The effect of rolling parameters on microstructure and tensile properties of nanocrystalline/microcrystalline 304 stainless steel (SS) casted by the aluminothermic reaction was investigated in this work. It was found that majority of the nanocrystalline austenite of the 304 SS rolled at 700 degrees C and 900 degrees C grew up and transformed to sub-microcrystalline. While the nanocrystalline/microcrystalline structure still retained rolled at 900 degrees C with 40% deformation followed 600 degrees C with 70% thickness reduction, and microcrystalline austenite grains distributed evenly. The strength and ductility of the various rolled 304 SS were improved compared with the as-casted 304 SS steel. The steel rolled at 900 degrees C with 80% deformation exhibited a uniform elongation as large as 31.3%, which is almost the same ductility level of counterpart coarse-grained steel. The rolled steel at 700 degrees C with 80% deformation achieved the maximum tensile strength but the smallest elongation. The sample, two-step rolled at 900 degrees C with 40% thickness reduction and then 600 degrees C with 70% thickness reduction, yielded the satisfactory combination of strength and ductility. The yield strength and elongation were appropriate 767 MPa and 22.8%, respectively, which resulted from the optimized nanocrystalline/microcrystalline structure and distribution.