Structure And Properties Of CrNiTiNbZr High Entropy Alloy

As the material specifications required in the engineering field are getting higher and higher,a new type of material has been introduced in the alloy industry-high-entropy alloys.It is prepared by smelting,sintering and other methods.In a high-entropy environment where many alloying elements are aggregated,the alloy is easily formed with a simple structure.In latest years,many scholars have paid much attention to the high-degree hardness,great decay resistance,terrific temperature stability and fabulous abrasiveness of high-entropy alloys.In this dissertation,the CrNiTiZrNb high-entropy alloy was manufactured by vacuum arc melting,and accordingly tackle annealing treatment on the foundation of the as-cast high-entropy alloy,after that,structural characteristics were analyzed by X-ray diffractometer,SEM and EDSto judge the difference in performance.in which the performance test is to use micro hardness tester,single ball friction and wear and high temperature carbon rod resistance furnace.The experimental structure effectively analyzes the phase structure,microstructure and composition of the as-cast alloy,and systematically analyzes the effect of annealing temperature on the properties of the alloy.Finally,the microhardness,wear resistance and high temperature oxidation resistance performance are analyzed.Good generalization on the test results.Among which,the white phase dendrite is Zr,Nb and NiZr₂ mixed solid solution BCC Mutually.The interdendritic phase is NiTi and Cr Ti₄,and the Ti-rich phase is distributed in the interdendritic.The microhardness of as-cast CrNiTiNbZr high-entropy alloy is 634.90HV.After annealing treatment,the microstructure at 600℃ and 700℃ is relatively uniform,and the content of black and dendritic white phases is similar to that of the as-cast state,and the gray phase is Ni solid solution and Cr-Ti-containing intermetallic compound.The phase structure of the high-entropy alloy annealed at 800℃is a simple solid solution,which is the least content among the four groups,and it is a simple solid solution of BCC1+BCC2.The peak value of microhardness in as-cast and annealed state is the maximum value of 786.40HV in 800℃.According to the wear test of the as-cast and annealed CrNiTiNbZr high-entropy alloys under drying and deionized water conditions,it can be concluded that there are three major effects due to deionized water:（1）Lubrication effect.Deionized water molecules can effectively isolate the friction surfaces from each other,effectively reduce the friction coefficient,and reduce the period of wear-in period.（2）Flushing effect.It can clean the debris and wear debris on the friction surface and reduce the damage caused by abrasive wear.（3）Cooling effect.As a good heat transfer medium,aqueous solution can effectively dissipate frictional heat and reduce the phenomenon of corrosion and wear.The as-cast and annealed CrNiTiNbZr high-entropy alloys have different degrees of abrasive wear and adhesive wear on the surface in a dry environment.The morphology shows that the abrasive particles and oxide particles are attached to the surface,and layered or scaly pits appear.with plough furrows.According to the high temperature oxidation resistance conditions of the as-cast alloy,the high temperature oxidation test of CrNiTiNbZr as-cast alloy was carried out at 500℃,600℃ and 700℃.The strongest,followed by 600℃and 700℃.There are about six kinds of oxidation products:Cr₂O_3,ZrO₂,Nb₂O₅,TiO₂,Ti₂ZrO₆and NiTiO₃.Among them,the oxidation product NiTiO₃in the600℃group proves that more Ni and Ti atoms are required for the oxidation behavior,and the oxidation rate is in the middle.For the phase analysis at 700℃,it was found that Ti₂ZrO₆ and NiTi O³ appeared more,and there were not enough Cr₂O₃ and TiO₂ to protect the inside of the metal.The study of annealed state adopts the principle of preference,and explores the high-temperature oxidation resistance behavior of annealed CrNiTiNbZr at 500℃.