Transformational, microstructural and superelasticity characteristics of Ti-V-Al high temperature shape memory alloys with Zr addition

This study analyzes the influences of Zr addition on the martensitic transformation behavior, microstructural evolution, mechanical properties and superelasticity effect of arc-melted Ti-12V-4Al-xZr (x = 0, 0.5, 1, 1.5 and 2 wt.%) high temperature shape memory alloys (HTSMA). The results revealed that the austenite transformation temperatures and activation energy values decreased linearly when the Zr addition was greater than 0.5 wt.%. The Ti-V-4Al (wt.%) and Ti12V-4Al-0.5Zr (wt.%) alloys were composed of alpha '' martensitic phase, while the others consisted of predominant alpha '' martensitic phase and a small amount of the beta austenite phase. The thickness of martensitic plates in the alloys reduced with increased Zr addition. Hardness and reduced elastic modulus values calculated from load-depth curves of the alloys also decreased with increasing Zr addition. Along with the increase in the Zr addition, the alloys' superelasticity behavior decreased at room temperature (24 degrees C), while this behavior increased at the high temperatures (450 degrees C).

Automated summary

The addition of Zr has significant effects on the performance and structure of Ti-12V-4Al high temperature shape memory alloys. As the Zr content increases, the austenite transformation temperatures and activation energy values decrease, the thickness of martensitic plates decreases, hardness and reduced elastic modulus values decrease, and the superelastic behavior weakens at room temperature but strengthens at high temperatures.