Tailoring the performances of Ti-V-Al base shape memory alloys by defects engineering

In the present study, various defects such as dislocations were controlled in Ti-V-Al-based shape memory alloy by thermomechanical treatment and introduction of interstitial oxygen (O) atom to optimize the performances. The results revealed that the Ti-V-Al-O shape memory alloys gradually evolved from alpha" martensite phase to the beta parent phase with increasing annealing temperature. Moreover, the degree of lattice distortion can be tailored by changing annealing temperatures. Upon the annealing temperature reached 900 C-degrees, masses of omega precipitates and a nano-sized ordered domain, characteristic of strain glass, can be found. As a result of suppression effect of multiple varieties of defects to the martensitic transformation, no obvious endothermic and exothermic peaks were observed in differential scanning calorimetry curves. The yield strength and maximum tensile fracture strength of the Ti-V-Al-O shape memory alloy increased with the increase of annealing temperatures. Meanwhile, Ti-V-Al-O shape memory alloys annealed at 900 C-degrees possessed superior strain recovery characteristics and corrosion resistance. The excellent performances in Ti-V-Al-O shape memory alloys annealed at 900 C-degrees can be attributed to the formation nanoscale nanodomain.