Research ArticleMATERIALS SCIENCE

Achieving room-temperature brittle-to-ductile transition in ultrafine layered Fe-Al alloys

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Science Advances  23 Sep 2020:
Vol. 6, no. 39, eabb6658
DOI: 10.1126/sciadv.abb6658
  • Fig. 1 The morphology and structure of FeAl and FeAl2.

    (A) Binary Fe-Al phase diagram (10, 14). The red dotted line indicates the alloy composition in this work. (B) Typical scanning electron microscope (SEM) micrographs of the FeAl alloy with both FeAl and FeAl2 phases. (C) Typical SEM image of the FeAl alloy with a layered morphology in which the bright phase is FeAl2 and the dark phase is FeAl. The thickness is defined as the total thickness of one layer of FeAl and one layer of FeAl2 (as marked in the figure). (D) Crystal structures of FeAl and FeAl2. (E) Typical TEM micrographs of the layered FeAl/FeAl2 alloy. (F) The selected-area electron diffraction pattern of the layered FeAl/FeAl2 alloy showing that it has an interface orientation relationship of [1¯10]FeAl2//[1¯11]FeAl and (113¯)FeAl2//(101)FeAl.

  • Fig. 2 Comparison of indentations.

    (A) Typical SEM micrographs of the indentation site in single-phase FeAl2. (B to F) Typical SEM micrographs of the indentations in the layered FeAl/FeAl2 with an average phase thicknesses of 2.5 μm, 1.5 μm, 1 μm, 500 nm, and 259 nm. The hardness is also labeled in the figure. HV is the unit for the Vickers hardness.

  • Fig. 3 Deformation of layered FeAl/FeAl2 (t = 2 μm).

    (A) SEM micrographs of an indentation on layered FeAl/FeAl2 with an average thickness of 2 μm. (B to D) Typical TEM micrographs showing the character of the slip bands in the FeAl2 phase. (E) Stress concentration induced–contrast at the interface in the FeAl layer. (F) Slip transmission pathway across the FeAl/FeAl2 interface.

  • Fig. 4 Deformation of layered FeAl/FeAl2 (t = 1.5 μm, 500 nm, and 259 nm).

    (A to C) TEM micrographs displaying the deformation microstructures underneath the indentation on a layered FeAl/FeAl2 with an average layer thickness of 1.5 μm. (D to F) TEM micrographs of the microstructures formed beneath the indentation on a layered FeAl/FeAl2 with an average layer thickness of 500 nm; slip localization and shear of the interface were identified. (G to I) TEM micrographs showing the deformation microstructures underneath the indentation on a layered FeAl/FeAl2 with an average thickness of 259 nm. Slip bands have developed across many alternating FeAl/FeAl2 layers.

  • Fig. 5 Deformation of layered FeAl/FeAl2 pillars.

    Typical SEM micrographs of the layered FeAl/FeAl2 pillars before (A, C, and E) and after (B, D, and F) compression. The three pillars in (A), (C), and (E) have different layer orientations relative to the loading axis. (G) Typical compressive stress-strain curves of the layered FeAl/FeAl2 pillars.

  • Fig. 6 GSFE curves of FeAl and FeAl2.

    (A) Unrelaxed (UR) and relaxed (R) generalized stacking fault energies (GSFE) curves in the B2-ordered FeAl calculated here. Also shown for comparison are the (UR) results based on prior ab initio calculations from Liu et al. (46) and Medvedeva et al. (47). (B) UR and R GSFE curves in FeAl2.

Supplementary Materials

  • Supplementary Materials

    Achieving room-temperature brittle-to-ductile transition in ultrafine layered Fe-Al alloys

    Lu-Lu Li, Yanqing Su, Irene J. Beyerlein, Wei-Zhong Han

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