Mechanical and Corrosion Properties of Fe-based Medium Entropy Alloys with minor element addition

Abstract:

The Fe_63.3Mn₁₄Si_9.1Cr_9.8C_3.8 and (Fe_63.3Mn₁₄Si_9.1Cr_9.8C_3.8)₉₉X₁(x=Ag,Cu,Ce) medium entropy alloys were fabricated by magnetic levitation melting and negative pressure copper mold suction casting method. The effects of adding 1% Ag, Cu and Ce on the microstructure, mechanical properties and corrosion resistance of the alloy were studied. After adding 1% of Ag, Cu, Ce, the alloy entropy value is between 1R and 1.5R, which belongs to the category of medium entropy alloy. The mixed alloy is negative, and the atomic size difference, electronegativity difference and valence electron concentration value are small so it has the single FCC structure. (Fe_63.3Mn₁₄Si_9.1Cr_9.8C_3.8)₉₉Ce₁ alloy has the largest δ and large lattice distortion energy. Ce has the best comprehensive mechanical properties by purifying the melt and grain refinement. The fracture strength is 2815 MPa, and the yield strength is 854 MPa, the elongation rate is 22.89%, and the maximum hardness can reach 658.4 Hv. The alloy system has lower energy, finer grains, and enrichment of rare earth Ce on the surface, so a dense and uniform passivation film is formed after corrosion. In (Fe_63.3Mn₁₄Si_9.1Cr_9.8C_3.8) ₉₉Cu₁, the Cu-rich phase and Cr-rich phase form micro galvanic cells. The Cu-rich phase will corrode preferentially, and Cu deteriorates the corrosion resistance of the alloy.