Bi-modal microstructure in a powder metallurgical ferritic steel

Ferritic steel with a nominal composition of Fe–14Cr–3W–0.42Ti–0.32Y was prepared by mixing gas-atomized prealloyed powder and mechanically alloyed powder. The microstructure is much different from other ferritic steels with the same composition and prepared via only mechanically alloyed powder. A bi-modal structure, which consists of pure ferritic grains and martensitic grains, was obtained after hot forging and air cooling. A phase transformation of αbcc → γfcc → α'bcc was also discovered in microstructural observation. The bi-modal microstructure shows a good combination of high strength and high ductility.