Microstructure And Mechanical Properties Of FeCrVTi-base High Entropy Alloys

High entropy alloy is a new conception of alloy design,this new design strategy aims at the maximization of the entropy with the purpose of producing massive solid solution,single phase microstructures,and also preventing the appearance of intermetallic compounds.The high entropy alloys have great performance on strength,hardness and high temperature mechanical properties.The component selection of high entropy alloys is flexible,the characteristics of each element can be fully elaboration which possesses a huge development potential.The structure material with good high-temperature resistant and anti-irradiation properties is the key to nuclear reactors.So high entropy alloys provide a new method of low activation materials.In this work,FeCrVTi high entropy alloy system was chosen to study the feasibility of the combination of high entropy alloy and low activation material.And as a new HEA system,the effect of different type and content of main elements on microstructure and mechanical properties were also researched.The main conclusions are as follows:Adding different elements of the equivalent mole-ratio FeCrVTi alloy system has great effect on microstructure and mechanical properties.And found the alloy is composed of BCC phase.The hardness is inversely proportional to its value of ?.And FeCrVTiMo high entropy alloy was brittle,mostly fracture in the elastic stage.FeCrVTiMo high entropy alloy is composed of BCC1 and BCC2 phases.And the result shows that with the rising temperature,the fracture type of the alloy changed and the compressive strength increases first and then decreases.After homogenizing,the ductility and compressive strength decrease slightly.The fine primary ? Ti precipitated during the aging process is the main reason for the sharply strength reduction of the alloy.Based on the VEC theory,the Fe_3.5Cr_1.2V_1.5Ti_1.5Mn₁X_0.3?X=Mo,W?alloy system was designed.The microstructure is well-distributed and the excellent compressive strength can be maintained at high temperature.The primary ? Ti phase and secondary ? Ti phase were precipitated after aging treatment.The compressive strength of the alloy can be improved by the small and dispersed secondary ? Ti particles.Secondary ? Ti phase became coarse with aging time increasing which has bad influence on compressive strength.Co MPared with FeCrVTiMo high entropy alloy,Fe_3.5Cr_1.2V_1.5Ti_1.5Mn₁X_0.3?X=Mo,W?alloy system has better mechanical properties after aging treatment.In order to obtain an alloy with better ductility,Fe₃₅Cr₂₀Mn₁₀Cu₂₅V₁₀ high entropy alloy was designed which has FCC crystal structure and with a 7.95 VEC value.It is found that the Fe₃₅Cr₂₀Mn₁₀Cu₂₅V₁₀ high entropy alloy is composed of a BCC parent phase and nano-sized copper rich precipitates.With a good ductility,the alloy did not fracture after yielding and the yield strength was 577 MPa.Due to the coarsening of FCC1 phase particles after aging,the yield strength of the alloy increased considerably.After 700? 1500 h aging treatment,the hardness and yield strength of alloy increased.