Martensitic Transformation And Shape Memory Effect Of Ti-V-Al Alloys

Shape memory alloys is widely used in the aerospace industry for its shape memory effect and superelastic. Ti-Ni alloy exhibits good workability and excellent recovery strain. But the density of Ti-Ni is above 6.5g/cm3, which is not suitable for the demand of weight reduction of aircraft materials. It is meaningful to research lightweight shape memory alloys.Ti-V-Al shape memory alloys get much attention for its low density and good shape memory effect. The density of Ti-V-Al alloy is below 5g/cm3. The content of V in Ti-V-Al alloy has a remarkable effect on the properties of the alloy. The influence rules and mechanisms of V content of Ti-V-Al alloy have not been investigated systematically. In this paper, the influence rules and mechanisms that how V content and themal-mechanical treatment effect the microstructures, martensitic transformation behavior, themal stability, mechanical properties and shape memory effect of Ti-(12,13,14,15,16,17)V-3Al alloys are systematically investigated by means of XRD, SEM, TEM, DSC and tensile test.The content of β phase in Ti-V-Al alloys increases with the increase of V content. When the V content is 13 at.%,the microstructure of Ti-V-Al is single phase of α?? martensite. When the V content is 17 at.%,the microstructure of Ti-V-Al is single phase of β. In the Ti-V-Al alloys, martensite variants are major self-accommodation morphology. In solution-treated Ti-V-Al alloys, the reverse transformation temperature(As) decreases with the increase of V content. Also the themal stability is enhanced by V content.In solution-treated Ti-V-Al alloys, the elongation increases with the increase of V content. With the increase of V content, the shape memory effect of Ti-V-Al firstly increases and then decreases. When the V content is 16 at.%, the alloy exhibits the max recovery strain with 6% pre-strain at room temperature. The max recovery strain can be as large as 5.4%. When the cold-rolled Ti-16V-3Al alloy with a thickness reduction of 70% annealed at temperature range from 650℃ to 800℃,the shape memory effect increases with the increase of the annealed temperature. The Ti-16V-3Al annealed at 800℃ exhibits the max recovery strain. The max recovery strain is 7.6% with the pre-strain 8% at room temperature.