Phase transitions in nanostructured Fe–Cr–Ni alloys prepared by mechanical alloying

Phase transition of Fe–18Cr–8Ni, Fe–15Cr–15Ni and Fe–15Cr–25Ni alloys during mechanical alloying (MA) and after subsequent annealing was studied. For Fe–18Cr–8Ni and Fe–15Cr–15Ni the resulting structure by MA was a nanostructured single-phase BCC solid solution (α) which differs from that predicted from equilibrium phase diagram. Furthermore, the equilibrium structure was not achieved after heat treatment at 700 °C for 1 h even at low cooling rate. In contrast the structure of Fe–15Cr–25Ni powder as-milled and after subsequent annealing was a fully austenite structure in consistent with the equilibrium phase diagram. These discrepancies can be explained by Cr and Ni alloying as well as nanocrystallization effects.