Interphase precipitation of Fe2Hf Laves phase in a Fe–9Cr/Fe–9Cr–Hf diffusion couple

Periodically arrayed rows of fine Fe2Hf Laves phase particles were found to form in ferritic matrix containing 9 weight percent chromium and a few weight percent hafnium. Microstructural investigation suggests that the particles were formed on cooling through interphase precipitation during the phase transformation from δ ferrite to austenite, and the austenite was subsequently transformed into the α ferrite. The interphase precipitation mode may be effectively used to strengthen ferritic heat resistant steels with Laves phase.