Effects of Heat Treatment on Microstructure and Electrochemical Corrosion Properties of the CrNbTiVAl1.25 Refractory High-Entropy Alloys
Due to the low degree of freedom of alloy composition in conventional alloys,a large number of brittle intermetallic compounds or intermediate phases with complex structure will precipitate inside the alloys,resulting in their limited mechanical properties and corrosion resistance.However,refractory high entropy alloys(RHEA),which are characterized by high disordered atomic arrangement,good mechanical properties and corrosion resistance,etc.,can be used to replace the traditional alloys in order to satisfy the requirement for the applications of new materials.In this paper,the microstructure and electrochemical corrosion characteristics of as-cast and heat-treated CrNbTiVAl1.25 RHEAs are investigated using X-ray diffraction(XRD),scanning electron microscopy(SEM),and electrochemical workstations.The results indicated that the as-cast alloy exhibits equiaxed crystal morphology and that its microstructure is composed of BCC,Laves,and β-Ti phases,with laves phase distributing at grain boundaries and β-Ti phase randomly distributing within each grain and grain boundaries.After being heat treated at 1050 ℃,the alloy is still composed of BCC,Laves,and β-Ti phases.The β-Ti phase distributes in blocks in the microstructure,and Laves phase distributes in blocks at grain boundaries.Electrochemical corrosion experiments show that the heat-treated CrNbTiVAl1.25 RHEAs have a larger corrosion potential and smaller corrosion current density,which significantly improves their corrosion resistance compared to the as-cast alloys.The heat-treated CrNbTiVAl1.25 RHEAs have a larger half arc and the largest impedance modulus,indicating that heat treatment is beneficial for improving the structural stability of the passivation film,which in turn improves the corrosion resistance of the alloys.
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