L1₂ precipitates within L2₁ ordered Fe–21.7Mn–14.5Al

Abstract

Needle-like precipitates exhibiting Widmanstätten side plate morphology have been observed in Fe–21.7Mn–14.5Al annealed at 1573 K for 2 h followed by furnace cooling. The precipitates were identified to be an L1₂ (ordered fcc) structure, whereas the matrix had an L2₁ (ordered bcc) structure. The orientation relationship between the precipitates and matrix was found, by electron diffraction analysis, to be (011)L2₁//(001)L1₂, [11]L2₁//[10]L1₂. Nanoindentation results showed that the hardness of the L1₂ phase was ∼10.2 GPa, whereas a hardness of ∼15.9 GPa for the L2₁ matrix was found.

Keywords:

• precipitation
• ordered intermetallics
• precipitation
• orientation relationship
• nanoindentation
• transmission electron microscopy

Acknowledgements

This research was supported by National Science Foundation Grants DMR 0552380 and 0905229. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or the US Government.