Original Article

The effect of Nb, Ta, and aging treatment on the properties of Ti₃₆Ni₄₉Zr₁₅ high-temperature shape memory alloy

¹ Department of Mechanical Engineering, Faculty of Engineering, Gazi University, Eti Mah. Yukselis Sk. No: 5, 06570, Maltepe/Ankara, Turkey
² Additive Manufacturing Technologies Research and Application Center-EKTAM, Gazi University, Saray OSB Mahallesi, Uzay ve Havacılık OSB Küme Evleri, No: 62 Kahramankazan, Ankara, Turkey
³ Faculty of Materials and Chemical Engineering, GIK Institute of Engineering Sciences and Technology, Topi - 23640, Pakistan
⁴ Department of Materials Science and Engineering, Institute of Space Technology, Islamabad, Pakistan

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 19 July 2025
Accepted: 9 December 2025

Abstract

TiNiZr high-temperature shape memory alloys (SMA), alloyed with niobium and tantalum for the composition Ti₃₁Ni₄₉Zr₁₅Ta₅ and Ti₃₁Ni₄₉Zr₁₅Nb₅, were aged at different temperatures. In both cases, the hardness increased with the aging temperature and peaks at 700 °C. Martensite structure appears during the aging treatment and grows with aging temperature. The transformation temperature exhibited different trends with the addition of niobium, tantalum, depending on the aging temperatures. With quaternary compositions, aging led to an increase in transformation hysteresis. A key attribute of this trend was the induced lattice strain with the quaternary addition of Ta and Nb, which led to a higher degree of undercooling. Additionally, higher temperature propagated the precipitation of the (Ti, Zr)₂Ni second phase in the matrix, which peaked for a limited time of 1 hr at 700 °C. The martensite morphology became coarser, indicating a significant grain growth and an overgrowth of the precipitates. The hardness values also peaked at an aging temperature of 700 °C, indicating that a highest volume of precipitation in the matrix.