Martensitic Transformation And Shape Memory Effect Of Ti-Nb-X(X=Ag、Co) Shape Memory Alloys

Ti-Ni shape memory alloy has been widely studied and applied because of its excellent memory effect and superelasticity,but its martensitic transformation temperature is low and its application is limited.Ti-Nb shape memory alloy has a wide martensitic transformation temperature range and excellent hot and cold process ability,but the shape memory effect needs to be improved.By adding Ag and Co elements to improve the shape memory effect of Ti-Nb alloy.In this paper,the influence rules and mechanisms that how Co,Ag content and themal-mechanical treatment effect the microstructures,martensitic transformation behavior,mechanical properties and shape memory effect of Ti84-xNb16 Agx alloys and(Ti84Nb16)100-xCox alloys are systematically investigated by means of XRD,SEM,TEM,DSC and tensile test.Co has a great effect on the phase transition temperature of solution treated(Ti84Nb16)100-xCox alloy,by increase 1at.% Co,the phase transition temperature decreases by about 60℃.The tensile strain of Ti84-xNb16 Agx alloy increases with the increase of Ag content,and the tensile strength decreases slightly.The solution treated(Ti84Nb16)100-xCox alloy The tensile stress increases with the increase of Ag content,and the tensile strength increases.The strain recovery property of Ti84-x Nb16 Agx alloy increases with the increase of Ag content.When the Ag content is 2at.%,the max recovery strain is 4.8% with the pre-strain 8%.When the Co content is 0.5at.%,the max recovery strain is 1.9% with the pre-strain 4% and the strain recovery rate decreases with the addition of Co content in the solution treated(Ti84Nb16)100-xCox alloy.The recoverable strain of Ti84-xNb16 Agx alloy increases first and then decreases with the annealing temperature increasing,and the best memory effect is obtained at750℃.750℃ annealing 1h in better than annealing 10 min and 4h,the max recovery strain is 6% with the pre-strain 8%.With the increase of Ag content,the rocovery strainof different heat treated Ti84-xNb16 Agx alloys become better.