Elemental effect on the phase formation and mechanical properties in the FeNiMnCuAlTi alloy system

Abstract

The FeNiMnCuAlTi alloys were prepared using the arc-melting method by varying the individual elements. The change in microstructure and mechanical properties of the alloys due to the changes in the elemental composition was carried out by X-ray diffraction, Scanning Electron Microscopy, and transmission electron microscopy. Equiatomic composition exhibited the B2_BCC and C_14 Laves phase, whereas increasing the Fe content in the alloys enhanced the formation of the BCC phase. Cu and Ni enhanced the formation of the FCC phase and the addition of Al and Ti favored the formation of intermetallics. Cu tends to segregate in the inter-dendritic region in all these alloys by forming a Cu-Mn-rich FCC phase. Fe, Ni, Cu and Mn-rich alloys showed good plasticity, whereas Al and Ti-rich samples are extremely brittle. A high compressive yield strength of 2016 MPa, 1526 MPa, and 1255 MPa was observed for the high-entropy alloys Fe30(NiMnCuAlTi)70, Ni30(FeMnCuAlTi)70, and Mn30(NiFeCuAlTi)70 respectively, with plasticity varying between 3% to 10%. Whereas medium entropy alloys showed a lower compressive yield strength but with increased plasticity e.g., a compressive yield strength of 1525 MPa and 27% plasticity for the case of Fe50(NiMnCuAlTi)50 was observed. The good combination of strength and plasticity is due to the presence of the FCC/BCC phase with a fine uniform distribution of intermetallic phases.