A NEW PHASE IN AN FE-9.0AL-29.5MN-1.2SI ALLOY

Abstract

A new type of precipitate (designated L phase) was observed within the ferrite matrix in an Fe-9.0Al-29.5Mn-1.2Si alloy after being aged at 550-degrees-C. Transmission electron microscopy examinations indicated that the L-phase precipitate has a monoclinic structure with lattice parameters a = 0.656 nm, b = 0.797 nm, c = 0.637 nm, and beta = 109.4 deg, and the orientation relationship between the L-phase precipitate and the ferrite matrix could be stated as follows: (1BAR01)alpha-parallel-to (001)L-phase (1BAR10)alpha-parallel-to (1BAR11)L-phase with a deviation of 0.3 deg (011)alpha-parallel-to (131)L-phase with a deviation of 1.5 deg The L phase has never been observed in various Fe-Al-Mn, Fe-Mn-Si, Fe-Al-Si, and Mn-Al-Si alloy systems before.