Novel Al-Co-Ni-Cu as-cast alloy with high damping and good corrosion resistance

A new multi-principal Al-Co-Ni-Cu alloy with high damping and good corrosion resistance was prepared. The effects of the Al content on the microstructure, damping properties, corrosion behavior, and mechanical properties of Al_xCoNi₂Cu (x = 0, 0.1, 0.3, and 0.5) alloys were studied. Al_xCoNi₂Cu (x = 0–0.5) alloys exhibited face-centered cubic (FCC) crystal structures. The Al_0.5CoNi₂Cu alloy displayed a significant increase in the internal friction (IF) value (Q⁻¹) compared to other Al_xCoNi₂Cu alloys (x = 0–0.3). The maximum Q⁻¹ of the Al_0.5CoNi₂Cu alloy was 0.032, which was twice that of Al_xCoNi₂Cu (x = 0–0.3) alloys and almost equal to that of the traditional Mn-Cu damping alloy. The mechanism for the sudden increase in the damping property of the alloys was explained by the interaction between the precipitated Ni₃Al phase and the dislocations generated during the nucleation process. Moreover, the Al_0.5CoNi₂Cu alloy exhibited a lower corrosion current and rate in electrochemical and immersion tests in a 3.5 wt% NaCl solution compared to Al_xCoNi₂Cu (x = 0–0.3) alloys. Supersaturated Al solubilized in the matrix, resulting in the formation of Al₂O₃ protective films which effectively delayed the corrosion process. In addition, the Al_0.5CoNi₂Cu alloy exhibited good corrosion resistance, comparable to that of ferritic stainless steel, making it a promising candidate for marine applications.