Microstructure And Properties Of CrVTaHf_xZrTi High Entropy Alloys

The total amount of steel lost due to corrosion every year in our country is almost equivalent to the annual output of a large steel mill.Research or design of corrosion-resistant alloys is urgently needed.The high-entropy alloy,which breaks the classic alloy design concept,has become a research hotspot in recent years because of its unique microstructure,high strength,high hardness and high corrosion resistance.In this paper,the CrVTaHf_xZrTi（x=0.2,0.4,0.6,0.8,1.0）high-entropy alloy is produced by non-consumable vacuum arc smelting.The phase composition and microstructure of the CrVTaHf_xZrTi high-entropy alloy are measured by scanning electron microscope and X-ray diffractometer.Test and analyze the structure and corrosion resistance.The study found that the phase structure of CrVTaHf_xZrTi（x=0.2,0.4,0.6,0.8,1.0）high-entropy alloy is mainly composed of BCC,HCP and a small amount of Laves phase（Ta V₂ and Ti Cr₂）;dendrite is rich in Ta,V,Cr The BCC phase of the elements and the HCP phase rich in Hf and Zr are between the dendrites;the as-cast CrVTaHf_0.4ZrTi alloy has the most intermetallic compound content,with the highest microhardness value of 937.42HV;after annealing at 700℃for 2h,the The Laves phase in the CrVTaHf_0.4ZrTi alloy is partially decomposed,and its alloy hardness is reduced.The grain distribution of other alloys in the alloy system after annealing treatment is more uniform,has a certain strengthening effect,and the microhardness of the alloy is improved.For the immersion corrosion experiment of CrVTaHf_xZrTi series high-entropy alloy,in the sulfuric acid corrosion solution with three concentrations of 0.5M,1.0M,and 1.5M,the corrosion rate of the alloy first decreases and then increases with the increasing content of Hf element.CrVTaHf_0.4ZrTi alloy Corrosion resistance is better than other alloys in the system;electrochemical test in sulfuric acid corrosion solution shows that CrVTaHf_0.4ZrTi alloy has a lower average corrosion rate and less pitting,the formed passivation film has good compactness,and the metal elements in the active zone diffuse Poor performance,showing excellent comprehensive corrosion resistance.After the CrVTaHf_0.4ZrTi high-entropy alloy is oxidized at 600℃,700℃,800℃for 50h,the main oxidation products are Cr Ta O₄,Ti Ta O₄,Cr₂O₃,Ti O₂,Zr O₂,Hf O₂,etc.The high temperature oxidation resistance of CrVTaHf_0.4ZrTi alloy is the best at600℃,but as the temperature rises,the oxide layer becomes thicker,the oxide layer formed is loose and porous,and the V₂O₅ generated in the alloy is easy to volatilize,which affects the alloy elements Concentration changes are not conducive to the high temperature oxidation resistance of the alloy,and the entire alloy is completely oxidized up to 800°C.