| High entropy alloy is a universally have high strength,high hardness and corrosion resistance and other excellent properties of the alloy,shape memory alloy because of its excellent shape memory effect and superelasticity in the transportation,aerospace,biomedical and other fields have great value of development and application.Combine"high entropy alloy"with"shape memory alloy",put forward the high entropy of memory alloy will each outstanding performance at an organic whole,Will be more able to adapt to life,industry and other higher and higher requirements.The element composition of high entropy shape memory alloys was studied.In this paper,five elements with good biocompatibility,Ti,Zr,Nb,Sn and Mo,were added,preparation the system of high entropy of memory alloy,The effect of varying alloy element content and conditions such as solid solution treatment on the properties of the alloy was investigated.This paper is based on the definition of the element composition of high entropy alloy,The five elements Ti,Zr,Nb,Sn and Mo were selected and prepared in atomic percentages Ti35Zr35Nb15+xSn10-xMo5（x=0,2.5,5）and Ti45-xZr40+xNb5Sn5Mo5（x=0,5,7.5）two systems of alloys.The effects of alloying element variation and solution treatment on microstructure,mechanical properties and superelasticity of the alloy were studied,and the influence of alloying element change on corrosion resistance of alloy.The microstructure was studied by optical microscope,electron microscope,energy spectrum analysis and X-ray diffraction spectrum.The mechanical properties and superelasticity of the alloy were analyzed by compression test,compression cycle test and hardness test.Corrosion resistance of the alloy was studied by electrochemical workstation.The main microstructure of Ti35Zr35Nb15+xSn10-xMo5（x=0,2.5,5）alloy at room temperature isα"martensite andβ-Ti.The increase of Nb content has a significant effect on the microstructure of the alloy.Nb15 of the alloy samples organization mainly for alpha"martensite,when the Nb17.5,it wasβ-Ti tissue.The alloy sample with Nb20 is a mixture ofβ-Ti and fineα"martensite.However,the alloy sample with Nb20 content is a mixed structure ofβ-Ti and fineα"martensite.The Nb15alloy whose main structure is martensite has the highest hardness and compressive strength The Nb17.5 alloy withβ-Ti structure has the best plasticity,and no fracture was observed in the compression experiment.Nb20 alloy have the mixture of the first two structures has moderate mechanical properties,but has better room temperature superelasticity.The results show that the microstructure and mechanical properties of the alloy are greatly affected by changing the contents of Nb and Sn.Ti45-xZr40+xNb5Sn5Mo5（x=0,5,7.5）alloy composed ofα"martensite andβ‐Ti structures.In addition to Ti45 alloy composed ofα"martensite and a small amount of mixed phase,the other two alloys are composed of mixed microstructure.The change of Ti content has little effect on the compression strength of the alloy,however,with the decrease of Ti content,the hardness of the alloy gradually decreases and the plasticity increases.Ti37.5 alloys withα"martensite andβ‐Ti structures and a few other mixed phases have the best plasticity.According to the cyclic compression test results with the increase of prestrain,it is found that the recoverable strain of the alloy can be increased with the increase of Ti content,and the superelasticity performance is excellent.Among them,the memory performance of Ti45 alloy is the best,and the ratio of superelastic recovering strain to recoverable strain is up to 33%.After different solution treatment（900℃for 2h,Quenching）Ti45-xZr40+xNb5Sn5Mo5（x=0,5,7.5）alloy and Ti35Zr35Nb15+xSn10-xMo5（x=0,2.5,5）alloy,there is no significant difference in microstructure between the alloy and the previous solid solution treatment（700℃for 2h,Quenching）,but the mechanical properties of the alloy are affected.The ductility of Ti45-x Zr40+x Nb5Sn5Mo5（x=0,5,7.5）alloys increases slightly only for Ti40 alloy,and decreases for the other two alloys,the compression strength of Ti45 alloy decreased obviously,and the hardness of other alloys increased.The plastic and compressive strength of Ti35Zr35Nb15+xSn10-xMo5（x=0,2.5,5）alloys are improved except Nb20 alloy,the hardness change is not obvious.Different solution treatments have little effect on the memory properties.Ti45 and Nb20 alloys are still the best superelasticity alloys in each system.It has been demonstrated that changing the Ti-Zr and Nb-Sn content has a significant modulating effect on the corrosion resistance of Ti Zr Zn Sn Mo high entropy memory alloy.The Ti37.5 alloy showed the lowest current density in the PBS simulated body solution and 3.5wt.%Na Cl solution electrochemical experiments,Ti35Zr35Nb15+xSn10-xMo5（x=0,2.5,5）alloy Nb17.5alloy with optimum corrosion resistance. |
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