Microstructure And Properties Of CrVNiAlCu High Entropy Alloy By Vacuum Arc Melting

The high-entropy alloy is a new type of alloy with high mixing entropy and excellent properties that breaks the limit of the number of single or double principal elements in the traditional alloy.It is prepared by mixing no less than five metal principal elements in equimolar or approximate proportions with each other.Practical prospects and research value.In this paper,a vacuum non-consumable arc melting furnace is used to prepare as-cast CrVNiAlCu high-entropy alloy samples,using X-ray diffractometer(XRD),scanning electron microscope(SEM)and built-in energy spectrometer(EDS),Vickers hardness tester(TMHV-1000),electrochemical workstation(CS350)and muffle furnace(SX2-6-13)on the phase composition and structure,microstructure,Vickers hardness,corrosion resistance and high temperature oxidation resistance of CrVNiAlCu high-entropy alloy,and Annealing treatment was carried out at 500?,600?,700?for 2 hours,and the effect and influence mechanism of different annealing temperature on microstructure and structure,Vickers hardness and corrosion resistance were studied and analyzed in comparison with as-cast alloys.The conclusions are as follows:1.The as-cast phase composition of CrVNiAlCu high-entropy alloy is a two-phase mixture of black and dark gray BCC rich Cr-V phase,gray and white FCC rich Cu-Ni phase.The black phase precipitates ordered B2 phase AlNi during annealing at600?.Metal compound,the Cr-V-rich black phase dissipates during annealing at700?,and the ordered B2 new black AlNi phase gathers in the gray phase and grows up in spheroidization.At the same time,there is strong lattice distortion in the dark gray BCC phase,VCrmetal compound Precipitation,the dark gray BCC phase microstructure dendrite preferentially grows and coarsens from lath to dendritic during annealing at 800?,and a large number of ordered B2 black AlNi phases nucleate and appear as tiny spheres dispersed in the gray phase,and there are also rich Decomposition of the Cu phase;the as-cast CrVNiAlCu high-entropy alloy has an overall Vickers hardness value of about 674HV.Annealing at 600? reduces the defects in the structure,and the alloy hardness is reduced to 534HV.After annealing at700?,AlNi and dark gray phase new lattice distortion are completely precipitated Increase the hardness to 552HV.The FCC phase decomposes during annealing at800? and the hardness value drops to 511HV;2.The as-cast CrVNiAlCu high-entropy alloy is resistant to Cl-ion erosion but not to nitric acid environment.The corrosion process occurs preferentially between the dendrites.The FCC phase rich in Al,Ni,and Cu is preferentially dissolved in the corrosive solution by corrosion,and deep corrosion holes appear to protect it.In addition to the BCC phase,the BCC phase is also corroded in concentrated nitric acid.After annealing at different temperatures,the potential difference formed by the different phases in the 3.5wt.%NaCl etching solution is reduced,and the corrosion resistance of the as-cast material is enhanced.Annealing at 800?The best time,the corrosion resistance of annealed alloy at 600?is greater than that after annealing at700?;3.The quality of the as-cast CrVNiAlCu high-entropy alloy is basically unchanged after being cyclically oxidized at 500?for 25 hours.The oxidation product of the matrix is simple and dense,while the oxidation at 600?produces a dense spinel CrVO₄ and Cu₅V₂O₁₀ mixed oxide outer layer,which protects the matrix from continuing to occur.Oxidation,the difference in thermal expansion coefficients of the inner and outer layers of the sample after the temperature rises to 700? causes the outer layer of oxide to fall off.The inner layer of oxide is Al oxide,which can also protect the matrix,but the oxidation resistance is not good.