Microstructure And Shape Memory Effect Of Thermomechanical Treated TiTaZrIn Alloy

TiTa alloy exhibits high phase transformation temperature and perfect workability,but it has poor thermal stability and insufficient shape memory effect.The Zr doping can effectively improve the thermal stability and shape memory effect of the alloy,but the incorporation of Zr leads to the decrease of the plasticity of the alloy.In this paper,In doping is used to improve the plasticity of the alloy and to improve the shape memory effect of the alloy by thermal-mechanical treatment.The effects of In doping and thermal-mechanical treatmenton on the microstructure,martensitic transformation,mechanical behavior and shape memory effect of TiTaZrIn alloy are investigated by means of XRD,SEM,TEM,DSC,bending method,and tensile tests.The results show that the solid solution Ti₆₅Ta_25-xZr₁₀In_x?x=0,1,2,5?alloys coexist with the?''+?phase at room temperature.With the increase of the content of In,the proportion of?''in the alloy increases.The Ti₇₀Ta₂₀Zr₁₀In₂ alloy is composed of a single?''martensite phase.It is found that[100]??[100]?''in Ti₆₅Ta_25-xZr₁₀In_x?x=0,1?alloys.The martensite variant in Ti₆₅Ta₂₃Zr₁₀In₂ alloy is?111?type I twin structure.In Ti₇₀Ta₁₈Zr₁₀In₂ alloy,the inner substructure of the large martensite variant is?111?type I twins.The addition of In can effectively improve the plasticity of the alloy.Compared with Ti₆₅Ta₂₃Zr₁₀In₂ alloy,the fracture strain of Ti₆₅Ta₂₃Zr₁₀In₂ alloy is increased from11.9%to 24.3%.The tensile strength of the alloy increased with the increase of In content.The strength of the alloy increased from 691.93 MPa to 802.34 MPa after incorporation of 5at%In.Ti₆₅Ta₂₃Zr₁₀In₂ alloy has the best shape memory effect,with the 6%prestrain,the maximum recoverable strain is 5.35%.Recrystallization of the cold rolled alloy after annealing at temperatures of 600?and above.The average grain size of the alloy increases with the increase of annealing temperature,and the average grain size of Ti₇₀Ta₁₈Zr₁₀In₂ alloy is about 40?m after annealing at 800?.There are a large number of dislocations in the alloys annealed at600?,and a large number of martensite plane can be observed after annealing at 800?,and the adjacent martensite variants are?111?type I twins.With the increase of annealing temperature,the plasticity of the alloy increased and the tensile strength decreased.The strength of the alloy annealed at 700?is sharp declined.The alloys annealed at 600?exhibits best shape memory effect,and Ti₆₅Ta₂₃Zr₁₀In₂ and Ti₇₀Ta₁₈Zr₁₀In₂ alloy can get a completely recoverable strain by 6%.With the prestrain of 7%,the maximum recovery strain of Ti₇₀Ta₁₈Zr₁₀In₂ alloy is 6.2%.