Study On Preparation And Properties Of FeCoNixMnTiy High Entropy Shape Memory Alloy

High Entropy Shape Memory Alloys（HESMAs）are a new type of functional alloy obtained by introducing the concept of high entropy into Shape Memory Alloys（SMAs）.They possess both high entropy properties and SMAs functions,thus having a wide range of application prospects and have been identified as potential new functional alloys.The project used the Spark Plasma Sintering（SPS）and high pressure sintering methods to prepare HESMAs.The phase composition and microstructure of the alloy were analyzed using X-ray Diffractometer（XRD）and Scanning Electron Microscope（SEM）.The effects of Ti/Ni content and sintering temperature on shape memory,corrosion resistance and mechanical properties of the alloy were investigated.Firstly,the effects of different Ti/Ni element contents on the structure and properties of Fe Co Nix Mn Tiy alloy under spark plasma sintering was studied.The study showed that an increase in Ti content would promote the enhancement of mechanical properties and shape memory properties of the alloy.However,as the Ti content continued to increase,the alloy experienced brittle fracture and decreased plasticity.However,an increase in Ni content will lead to a decrease in the mechanical and shape memory properties of the alloy,and an enhancement in its corrosion resistance.Fe Co Ni Mn Ti HESMAs with equal molar ratio have excellent comprehensive properties,with a shape recovery rate of 80%under 10%pre-strain.The yield strength and fracture strength of the alloy are 1450MPa and 2374MPa,respectively,with a vickers hardness value of 580HV.Secondly,the effects of different sintering temperatures on the various properties of Fe Co Ni Mn Ti_0.5 HESMAs were studied.The research results showed that as the sintering temperature increased,the mechanical and corrosion resistance of the alloy increased,while the shape memory performance decreased.However,as the temperature continued to rise,the alloy experienced overflow,leading to a sharp decrease in density and a deterioration in mechanical properties.Fe Co Ni Mn Ti_0.5HESMAs sintered at 950℃exhibit a shape recovery rate of 78.5%,yield strength of1129MPa,and fracture strength of 1475MPa under 10%pre strain.Finally,the effects of different sintering temperatures on Fe Co Nix Mn Tiy（x=1,1.33;y=1,1.33）HESMAs under high-pressure sintering was studied.The research results found that most of the alloy sintered bodies developed cracks due to the presence of residual stress,and brittle fracture occurred at room temperature compression,resulting in poor performance.Only Fe Co Ni_1.33Mn Ti alloy powder sintered at 950℃produced alloy blocks with plastic fracture.However,the yield strength and fracture strength of this alloy were not high,at 926MPa and 1170MPa,respectively,and at a pre strain of 5%,Its shape recovery rate was only 30%.