Microstructure evolution and mechanical behavior of as-cast, heat treated and directionally solidified Fe–15Al–10Nb alloys

•Microstructure was duplex or fully eutectic, depending on the processing conditions.•Hardness of the Laves phase was 16.4 GPa, four times higher than austenitic matrix.•AC alloy had the yield highest strength, followed by the HT and DS alloys.•All alloys showed good fracture toughness between 25 and 31 MPa m1/2.•DS alloy had lower creep resistance than the AC and HT alloy at 700 and 800 °C.

Fe–15Al–10Nb (at.%) alloys containing Laves phase fibers embedded in a disordered α-(Fe,Al) matrix were investigated in as-cast, heat treated and directionally solidified condition. Microstructure consisted of either duplex structure of primary dendrites and eutectic (as-cast and heat treated) or fully eutectic structure (directionally solidified). Nanoindentation on the Laves phase fibers revealed their anisotropic features as well as the onset of dislocation plasticity. Compression testing showed the yield strength anomaly, which occurred in the 500–650 °C range. Directional solidified alloy exhibited the lowest strength fracture toughness whereas the as-cast alloy had the highest strength and fracture toughness. The value of stress exponent obtained from the strain rate dependence of the flow stress indicated that the dislocation climb mechanism dominated the creep process. Deformation mechanisms were also discussed and related to the microstructure evolution.

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