Phase evolution and mechanical properties of non-equiatomic Fe–Mn–Ni–Cr–Al–Si–C high entropy steel

Abstract

Non-equiatomic FeMnNiCrAlSi–C high entropy steel was synthesized by mechanical alloying (MA) followed by spark plasma sintering (SPS). The effect of MA with milling time on phase formation and microstructural evolution was analyzed by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The dissolution of the elemental peaks with milling time and formation of the solid solution phase was followed systematically. The formation of a metastable BCC phase (a = 2.91 ± 0.02 Å) was observed after 40 h of milling. The average particle size of the 40 h milled powder was varying in the range of ∼ 8–10 μm. SPS of the 40 h milled powder at 1000 °C showed the phase transformation. The single-phase BCC structure was transformed into the FCC (austenite type) (cF4) (a = 3.58 ± 0.01 Å), B2 (cP2) (a = 2.87 ± 0.02 Å), Cr3Si (cP8) (a = 4.54 ± 0.04 Å) and Cr23C6 (cF116) (a = 10.62 ± 0.03 Å) phases. The spark plasma sintered sample had shown the density of 6.8 g/cm3. Hardness and wear properties of non-equiatomic FeMnNiCrAlSi–C high entropy alloy was determined by Vickers hardness and pin-on-disk system respectively. The alloy had shown the hardness of 596 HV with wear loss (rate) of 1.7 × 10−8 mm3/m. This high entropy alloy steel requires more investigation to classify them as a wear-resistant material.