Effects of the Addition of Iron and Chromium on the Structure and Properties of the Ni-Co-Mn-In Alloy

In this work, small amounts of Fe or Cr were added to Ni₄₇Co₃Mn_36.5In_13.5 alloy (x = 0) to produce five-component alloys with nominal compositions of Ni₄₇Co₃Mn_35.5In_13.5Fe₁, Ni₄₇Co₃Mn_33.5In_13.5Fe₃, Ni₄₇Co₃Mn_35.5In_13.5Cr₁, and Ni₄₇Co₃Mn_33.5In_13.5Cr₃, which are denoted as Ni₄₇Co₃Mn_36.5-xIn_13.5Fe_x/Cr_x (x = 1, 3 at.% Cr/Fe) series or as Mn-series (due to the addition of alloying elements instead of Mn), and Ni₄₇Co₃Mn_36.5In_12.5Fe₁, Ni₄₇Co₃Mn_36.5In_10.5Fe₃, Ni₄₇Co₃Mn_36.5In_12.5Cr₁, and Ni₄₇Co₃Mn_36.5In_10.5Cr₃, denoted as Ni₄₇Co₃Mn_36.5In_13.5-x (x = 1, 3 at.% Cr/Fe) series or In-series (due to the addition of alloying elements instead of In). The polycrystalline alloys were produced using the vacuum arc melting technique. The as-received alloys were characterized in structure, homogeneity, phase composition, martensitic transformation, and microhardness. The results showed that the addition of 1 at.% of Cr or Fe positively impacted the microstructure of the alloys. The quaternary alloy exhibited a single-phase coarse-grained structure. The addition of Fe and Cr (1 at.%) caused microstructure refinement with small Fe/Cr- and Co-rich γ particles appropriately distributed in the matrix, while the addition of 3% Fe or Cr resulted in γ formation in a dendritic form distributed more randomly. The addition of 1 at.% and 3 at.% of Cr or Fe significantly influenced the martensitic transformation temperatures. The microhardness increased by 21% in the Ni₄₇Co₃Mn_33.5In_13.5Fe₃ alloy compared to the quaternary alloy.