Directed energy deposited Fe36Ni35Al17Cr10Mo2 eutectic high entropy alloy: Hierarchical microstructure and tensile properties

Abstract

Eutectic high entropy alloy (EHEA) has attracted much attention due to its outstanding properties, which are commonly fabricated through conventional manufacturing methods. Additive manufacturing (AM) techniques that can create near-net components provide opportunities for rapid prototyping EHEAs. This study elucidated the microstructural evolution mechanisms of Fe₃₆Ni₃₅Al₁₇Cr₁₀Mo₂ EHEA fabricated by directed energy deposition (DED) via XRD, SEM, and EBSD. The dual-phase dendrite structure, micro-scale heterogeneous grains, and nano-scale BCC phases collectively formed the hierarchical microstructure in the DEDed alloy. We used neutron diffraction to demonstrate texture components and their relation to mechanical behaviors. {013}<100> texture possesses the highest Schmid factor compared to other textures, causing texture-induced softening of the FCC and B2 phases during tension. {233}<0 $\bar{1}$ 1> texture exhibits the low SF and hard orientation for the B2 phase. Due to the synergistic plastic deformation between FCC and B2 phases and precipitation strengthening from the BCC phases, the DEDed Fe₃₆Ni₃₅Al₁₇Cr₁₀Mo₂ exhibits an ultimate strength of ∼1267 MPa with an elongation of ∼20.1 % at room temperature. Moreover, the elevated-temperature tensile testing and crack analysis were employed to indicate the elevated-temperature fracture behaviors. We found that the nucleation and propagation of microcracks were suppressed at the phase boundary at elevated temperatures, avoiding brittleness and achieving excellent high-temperature mechanical properties. These results are expected to open ever-bright prospects for additive manufacturing Co-free high-performance EHEAs.