Effects Of The Element La On The Corrosion Behaviors Of CrMnFeNi High Entropy Alloys In Aqueous Solution

As a new type of alloy system,high-entropy alloys（HEAs）can form a single-phase solid solution by mixing with equal atomic ratios,and exhibit a series of excellent properties,which greatly expands the ideas and directions of exploration and development of new high-performance alloys.At the same time,the possibility of combining a variety of corrosion-resistant elements to form a single-phase solid solution also provides a new idea for design a new generation of high-performance corrosion-resistant alloys.It is worth noting that there is almost no research on the effect of the rare earth（RE）elements on the corrosion performance of HEAs.In this paper,the CrMnFeNi HEAs was selected,and by adding a small amount of lanthanum element,the key issues such as its corrosion resistance and corrosion mechanism have been studied in depth.It also provided some ideas and references for the desgin of RE-containing HEAs.The following were the main contents and conclusions of this article:1.The microstructure and morphology of the as-cast CrMnFeNi and CrMnFeNi La_0.004HEAs were studied and analyzed by XRD and SEM.Five concentrations of acid,chlorine-containing and alkaline aqueous solutions were selected to study the electrochemical corrosion behavior of the HEAs.The composition of the passivation film of the HEAs in acid solution was studied and analyzed by the XPS tests.The results show that the addition of La has a significant effect on the anodic polarization behavior of CrMnFeNi HEAs in acidic solution.2.Compared the electrochemical corrosion behavior of as-cast and equiaxed CrMnFeNi and CrMnFeNi La_0.004HEAs in 0.5 M H₂SO₄,1.0 M NaCl and 1.0 M Na OH solution,it was found that the addition of La significantly improved the resistance of CrMnFeNi HEAs in acid solution.The effects of rare element La on the corrosion and passivation behavior of CrMnFeNi HEAs in 0.5 M H₂SO₄ solution were studied by potentiodynamic polarization,M-S analysis,EIS and XPS analysis.3.The structure and composition of the HEAs passivation films were studied by film formation at different potentials and immersion tests.It was found that the addition of lanthanum significantly affected the composition of the CrMnFeNi HEAs passivation film.The immersion test results show that the addition of La effectively reduces the corrosion rate of CrMnFeNi HEAs in 0.5 M H₂SO₄ solution.The analysis shows that the presence of La has a significant effect on the pitting corrosion propagation of CrMnFeNi HEAs.