Study On Microstructure And Properties Of Al_xCoCrFe_1.2Ni High Entropy Alloy

In this paper,Al_xCo Cr Fe_1.2Ni high entropy alloy is taken as the research object.The microstructure,hardness,corrosion resistance and wear resistance of the high entropy alloy are studied by changing the content of Al element,remelting and annealing treatment,and adding 20%Co Cr Ni medium entropy alloy.The results provide a theoretical basis and method for promoting the application of high entropy alloy in wear and corrosion resistant materials.The specific research conclusions are as follows:The effect of Al element on the microstructure,hardness and wear resistance of Al_xCo Cr Fe_1.2Ni（x=0.4,0.7,1.0,1.3）high entropy alloy was studied.With the increase of Al content,the high entropy alloy transits from a single FCC phase to a mixed phase of FCC and BCC/B2,and finally to a BCC/B2 phase.The metallographic structure changes from columnar or cellular dendrites to equiaxed crystal.The increase of Al content increases the lattice transformation,improves the hardness of high entropy alloy,reduces the wear quality and improves the wear resistance.The effects of annealing temperatures of 600℃,800℃and 1000℃on the microstructure and properties of as-cast Al_1.0Co Cr Fe_1.2Ni high entropy alloy were studied.The effect of annealing at 600℃on the structure and properties of high entropy alloy is not obvious.After annealing at 800℃σPhase precipitation,the hardness of the alloy increased,and the wear resistance of the alloy increased.After annealing at 1000℃,the alloy is FCC and BCC/B2 mixed phase,and the pitting resistance is improved.The Al_1.0Co Cr Fe_1.2Ni high entropy alloy was remelted,and the microstructure,hardness,corrosion resistance and wear resistance of as-cast and the remelted high entropy alloys were compared and analyzed.The phase structure of the remelted high entropy alloy has no obvious change,and the microstructure is still equiaxed crystal,but the grain grows obviously,the grain boundary area decreases;EDS results show that the elements of the remelted Al_1.0Co Cr Fe_1.2Ni high entropy alloy have rediffused,with more uniform distribution,improved corrosion resistance（corrosion current density decreased by 0.1868μA/cm2）and decreased wear resistance.The Al_1.0Co Cr Fe_1.2Ni/Co Cr Ni（20%）composites were prepared.Compared with the as-cast Al_1.0Co Cr Fe_1.2Ni high entropy,FCC phase was formed in the composites,and the grain size grew,and the internal microstructure changed obviously.EDS results show that the accumulation of Cr is obvious and the content of Al is less at and near the grain boundary,which improves the pitting resistance of the composites in simulated saline-alkali solution.