Structural refinement and property optimization in an Fe-23Cr-8.5Ni duplex stainless steel

An Fe-23Cr-8.5Ni duplex stainless steel was used to prepare samples with different volume-fraction-weighted grain sizes (d(alpha gamma)), ranging from the nano-scale to the micrometer-scale by cold rolling and subsequent annealing. The cold rolled sample with d(alpha gamma) of 72 nm showed a high yield strength of about 1.3 GPa but only a small tensile elongation. An abrupt increase of ductility was observed as d(alpha gamma) increased to 375 nm, resulting in a good combination of yield strength of 738 MPa and tensile elongation of 29%. Further increase of d(alpha gamma) up to the micrometer-scale results in continued decreases in yield strength but with only a limited improvement in the ductility.