Research On The Structure And Properties Of AlCoCrFeMoNi Series High-entropy Alloys

High entropy alloy is a kind of multi-principal component alloy developed in recent years.The design idea of the alloy has broken the design way of a thousand years of alloy design with one or two elements as the main element,and opens up a new field of alloy design.And in performance,the high entropy alloy is obviously superior to the traditional alloy.However,at present,high entropy alloys are still in exploratory stage.And it is still far from the commercial application of high entropy alloy because of its immature theory and application.Therefore,it is necessary to concentrate on the research of high entropy alloys which have potential applications in some fields.The solution strengthening effect and hysteresis diffusion effect of high entropy alloy are beneficial to the thermal stability,high temperature softening resistance and high temperature strength of the alloy.In order to explore the high entropy alloy with high temperature resistance potential and application,AlCoCr₂FeMo_0.5Ni high entropy alloy is first studied in this paper.It is reported that the hot hardness and thermal stability of the alloy are superior to that of Inconel 718 Ni-based superalloy.However,it is found that the high entropy alloy AlCoCr₂FeMo_0.5Ni has severe brittleness at room temperature.Its microstructure is composed of a large number of brittle?phases and NiAl intermetallic compounds,and it is difficult to improve the ductility of the alloy by heat treatmen,so the alloy is difficult to be used as structural material at this stage.Aiming at the big data system,the single research form of high entropy alloy and the defects of traditional trial and error method,this article adopts a novel design form of high entropy alloy,A_xB_yC_{?100-a-b-x-y?}D_aE_b...,?This form can set the principal components of D,E...according to the performance requirements.And the content of the principal component of A,B,C can vary between 0%and 50%to achieve synergistic action?,and combining with the criteria of phase formation of high entropy alloy,using high flux calculation method to design 4 kinds of newly high entropy alloy and study.The results are as follows:?1?The microstructure of the four new high entropy alloys are all in line with the expectation,and AlCoCrFeMo_0.05Ni₂ alloy has excellent mechanical properties and high temperature resistance potential.Its microstructure is composed of FCC,BCC structure solid solution and nano-precipitated phase with BCC structure.The tensile strength of the as cast alloy at room temperature is 970 MPa,and the high temperature tensile strength at 700?is 640 MPa.?2?Comparing the microstructure and properties of the alloy in forging state and as cast state,it is found that the microstructure of the alloy is significantly refined,the strength and plasticity is greatly improved,tensile strength is 1208MPa,elongation is 25%.?3?After solid solution and aging treatment of AlCoCrFeMo_0.05Ni₂ high entropy alloy,it is found that a large number of needle-like phases are precipitated in the alloy,and with the increase of temperature,the precipitate phase coarsened and the hardness of alloy decreased.Because of the dispersion strengthening of the new phase,the alloy has obvious aging hardening phenomenon.The best aging hardening effect is obtained between 650?and 700?.The nano precipitated phase of BCC structure is coarsened and grown after aging treatment,and it is aggregated to the grain boundary to form?phase,which results in embrittlement of the alloy.?4?After aging at 680?for 8 h,the tensile strength,yield strength and tensile elongation of Al CoCrFeMo_0.05Ni₂ high entropy alloy can reach 1393 MPa,1080MPa and 19.5%,respectively.The alloy has excellent thermoplasticity at high temperature.After aging at 700?for 150h,the tensile elongation at 700?can reach 80%.