Study On The Microstructure And Properties Of Al_xCrFeMn_0.8Ni_2.1Zr_y High-entropy Alloys

AlCoCrFeNi_2.1 eutectic high entropy alloy has been widely concerned by researchers because of its excellent mechanical properties.In this paper,the high entropy alloy of Al_xCrFeMn_0.8Ni_2.1 system was obtained by using Mn element instead of expensive Co element,and Zr element was added to the alloy in order to further improve the mechanical properties of the alloy.In this paper,Al_xCrFeMn_0.8Ni_2.1 and Al_xCrFeMn_0.8Ni_2.1Zr_y alloys were studied by means of X-ray diffractometer,scanning electron microscope-energy spectrometer,electrochemical workstation and universal electronic testing machine.The corrosion properties,room temperature mechanical properties and microstructure evolution of Al_xCrFeMn_0.8Ni_2.1 alloy during annealing,as well as the microstructure and tensile properties of Al_xCrFeMn_0.8Ni_2.1Zr_y alloy at room temperature were studied systematically.The purpose of this paper is to provide a reliable theoretical basis for the practical application of high entropy alloys.The main conclusions of this paper are as follows:With the increase of Al content,the corrosion resistance of AlxCrFeMn_0.8Ni_2.1 high entropy alloy in 1mol/L sulfuric acid solution and 1mol/L sodium hydroxide solution decreased gradually.Under the experimental conditions,the corrosion resistanc e of the alloy in sodium hydroxide solution is better than that in sulfuric acid solution.With the increase of Al content,the hardness of Al_xCrFeMn_0.8Ni_2.1 alloy increases,the strength increases at first and then decreases,and the plasticity decreases gradually.After annealing at 900 C for 50 hours,it was found that BCC phase precipitated and annealed twins were formed in Al_0.2CrFeMn_0.8Ni_2.1 alloy,the amplitude modulation structure on Al_0.8CrFeMn_0.8Ni_2.1 alloy was spheroidized,and the coarse solar flower-like structure and interdendritic chrysanthemum-like structure disappeared on Al_1.0CrFeMn_0.8Ni_2.1 alloy,and fishbone structure appeared.After annealing at 900 C for 100 h,it is found that the BCC phase and annealing twins in Al_0.2CrFeMn_0.8Ni_2.1 alloy increase,the amplitude modulation structure of Al_0.8CrFeMn_0.8Ni_2.1 alloy disappears and grows further,and the fishbone dendrite of Al_1.0CrFeMn_0.8Ni_2.1 alloy grows further.Under the experimental conditions,the main form of Zr element in Al_xCrFeMn_0.8Ni_2.1Zr_y alloy is Laves phase,which exists in the interdendrite.With the increase of Al content,the hardness of Al_xCrFeMn_0.8Ni_2.1Zr_0.02 alloy increases,the strength increases at first and then decreases,and the plasticity decreases gradually.With the increase of Zr content,the hardness and strength of Al_0.2CrFeMn_0.8Ni_2.1Zr_y alloy increase,while the plasticity decreases.