Study On Microstructure And Properties Of CrFeCoNiTi_x High Entropy Alloy Prepared By Powder Metallurgy

High entropy alloy?HEAs?is a new kind of alloy proposed by Professor Ye Junwei's team based on the design idea of mixing a large number of equal or near equal atoms.The number of components of high entropy alloy elements is generally greater than or equal to 5,and each element has a large atomic fraction?between 5%and 35%?.Compared with other traditional alloys,high entropy alloys have excellent properties such as high hardness,high strength,good thermal stability,corrosion resistance and so on.Therefore,high entropy alloys are strongly used as potential structural materials.In this paper,five kinds of metal element powder of Cr,Fe,Co,Ni,Ti?purity>99.5%?were mixed according to the ratio of experimental design.First of all,mechanical alloying was used to prepare the raw powder,then powder metallurgy sintered the mixed powder to prepare CrFeCoNiTi_x?x=0.2,0.4,0.6,0.8,1.0?system high entropy alloy.Finally,the high entropy alloy was prepared by XRD,SEM,EDS,respectively.The microstructure and physical and chemical properties of Vickers hardness,electrochemical corrosion and nitric acid corrosion were studied by metallographic microscope.The experimental results show that the crystallinity of CrFeCoNiTi_x high entropy alloy powders with milling time of 10h is mainly FCC and part of BCC,FCC,and the particle distribution and size are relatively uniform and irregular shape.The bulk of CrFeCoNiTi_x high entropy alloy with sintering temperature of 1300?is mainly FCC.The element of Cr is distributed uniformly on the surface of bulk,the three elements of Fe,Co,Ni are mainly enriched on dendrite,and the element of Ti is mainly enriched in dendrite.Due to the increase of Ti content,the particle size of the ball-milling powder decreases;Part of the secondary phase is produced in the sintered block,the grain size decreases gradually,the lattice distortion becomes larger and the solid solution phase at the dendrite increases gradually;The hardness value of CrFeCoNiTi_x high entropy alloy increased gradually,when x=1.0,the maximum hardness value of CrFeCoNiTi_x high entropy alloy was 643.8HV;The electrochemical corrosion resistance of CrFeCoNiTi_x high entropy alloy was improved to a certain extent and then weakened,when x=0.6,CrFeCoNiTi_x high entropy alloy had the best electrochemical corrosion resistance;The corrosion resistance of CrFeCoNiTi_x high entropy alloy to 10wt%HNO₃ was increased to some extent,and then weakened,and when x=0.6,the CoCrFeNiTix high entropy alloy had the best corrosion resistance to 10wt%HNO₃;The corrosion resistance of CrFeCoNiTi_x high entropy alloy to 20wt%HNO₃ is decreasing gradually,and when x=0.2 CrFeCoNiTi_x high entropy alloy has the best corrosion resistance to20wt%HNO₃.