Analytical transmission electron microscopy study of grain boundary precipitates in an Fe–Ni–Mn maraging alloy

Field-emission gun analytical transmission electron microscopy was used to study grain boundary precipitates in Fe–10Ni–7Mn (wt.%) maraging alloy after isothermal aging at 753 K. High spatial resolution energy dispersive X-ray spectroscopy was used for quantitative chemical analysis of the grain boundary precipitates. Precipitation of f.c.t. θ-NiMn intermetallic compound and reversion to f.c.c. austenite were identified at prior austenite grain boundaries after prolonged aging. Selected area electron diffraction patterns (SADPs) showed the L10 type ordering of f.c.t. θ-NiMn precipitates. The f.c.t. θ-NiMn precipitates showed higher Ni and Mn concentrations than reverted f.c.c. austenite.