Microstructure of as-cast ASTM A 890-5A duplex stainless steel (Fe-_0.03%C-_1.5%Mn- _1%Si-25%Cr-7%Ni-4.5%Mo-0.2%N) in the solution-annealed condition. Etched with LB1 (100 mL water, 20 g NH4FHF, and 0.5 g K2S2O5). Austenite is colored, and ferrite is unaffected. Because it is as-cast, there are no annealing twins in the austenite. The magnification bar is 100 lm long.